All right...that's fair and I think my reasoning behind all of this is not clearly stated...Let's see if I can try and clarify some things...I feel like I should provide some background so you guys understand my concerns a little better...
Aside from all of my car modification history, I started off in racing as the electrical and engine management engineer on a Formula SAE team. I saw first hand what custom work, lack of testing, poor engineering judgement, poor team management, lack of preparation, scope creep etc does to a racing team. I would classify the results of this endeavor from a racing point of view as a 'complete failure' for a number of reasons many of which related directly to unrealistic requirements set forth by the team management.
Fast forward to two years ago, I raced a B4 2.2T 20v 5cyl Avant in Targa Newfoundland. This started off as a 2.0 FWD imported Avant that I decided to build up for the rally (
http://motorgeek.com/viewtopic.php?f=6&t=39033). During the 6 months it took me to build the car, I was constantly battling with ****ty customer service, custom one-off parts, hard to source and rare components, sole source purchasing etc etc. Due to supplier incompetence, I was left with less than two weeks to test a brand new build. Needless to say that's not enough time to test the car, let alone train the driver (me). A week later in Newfoundland, I threw the car face first into a 10ft ditch and destroyed pretty much everything I could.
This was a practice stage before the race even started. I`m not going to go into much details on what work was required to keep this car working for the rest of the week but flying control arms in from Ottawa that night was one of the easiest tasks. I think you get the point.
Here's something interesting I came up with at work recently - the difference between "lessons learned" and "lessons identified". A lesson is not learned until you've taken steps to avoid the event from reoccuring.
So here's a lesson identified and then learned when it comes to racing: "Never build or race a custom one-off piece of equipment unless you have the pockets to support it". I can give you endless examples from racing that all point to the same conclusion. The difference between professional racing teams and most of us is we can't afford to spend 100k and have a spare sequential transmission just sitting there for the swap.
With this in mind - let's look at this engine. I do not disagree with any of the points above. If I had an unlimited budget, I'd have 2 BHW engines built to the same spec with 2 quattro trannies ready to go. I don't, and even if I did I'd never throw away 40k on a week of racing again (lesson learned). The complete AHU has cost me a grand total of 200$ (including block, head, wiring, ecu, turbo, all manifolds etc) and I could probably find it for cheaper if I tried hard enough. Unfortunately, people put too much value on ALHs so I'd have to fork out upwards of 1k for a working engine with a good probability the mileage would be over 2-300k. ALH would be perfect. BEW would be perfect and so would BHW. Let's face it - they're not readily available and they cost money. I have a BEW in my Jetta that I got for next to nothing and I still won't pull it to swap into a race car.
Now - assuming AHU and ALH are the only cost effective choices, and I have an AHU handy, how can I limit the amount of custom work required to fit the AHU? Well...I just so happen to know that an AEG and AWM use the same block as an ALH (ie same mounting etc)...I also happen to know that 20v heads can be fitted to an ABA so there should be a way to do the exact opposite - fit an AHU head onto an AEG (or 1.8T block). All right - we've made some assumptions - now let's make some calculations..Can this actually work?
Well - the AEG has a pretty big bore and no oil squirters. It will need custom pistons (mucho $$) or I`ll have to dig up some T4 pistons. The 1.8t has an 81mm bore so I can find pistons for it relatively easy. With this in mind, what is affected by using these bottom ends? Well - the stroke of the engine and the displacement etc etc etc...
So you see, I`m not building a new engine to reduce the stroke. On the contrary, I`m trying to find the cheapest easiest solution to mating the TDi to my A4 that is repeatable time after time. The reality is - if this works, A LOT of people are going to enjoy the benefits - the same way the 20/20 gas hybrid was put together from a diesel crank and some custom pistons etc etc...There's merrit to doing some of this work - it costs nothing, gets your gears turning and there might be positive results.
As an example - when I was working on the B4 and wanted to run a quattro - EVERYBODY said it's impossible, it's too much work, way too expensive etc etc. If I had listened to the internet, I would have left it at that and moved on. Instead I investigated a little and found out that the B4 chassis is completely identical between the FWD and quattro version and the rear driveline is a direct swap with the exception of one bracket. All in all the swap cost me 50$ for welding a bracket.
Most of you guys here pride yourself with pushing the envelope and thinking outside the box. Without that, most of our projects would be damn boring. Can you honestly tell me that somebody's tried this swap and it doesn't work? If you could, you would have already. I have complete ABA, AHU, AEG, AWM and AEB engines sitting in the garage - why not do a little bit of poking? Worst thing that's going to happen is I`ll realize it's too much work and just weld two mounting brackets together. Same with the turbo - just because EVERYBODY uses VNTs, doesn't mean that's the only option. Worst that can happen is I realize you're right and a WG turbo is silly, but if nobody's tried it you can't make a factual analysis or recommendation for that matter.
Holy **** - this got long. Sorry - I`m using this to sort my own thoughts out as well.
On the question of spares:
1. Transmission
2. Driveshafts - ALL of them
3. Control arms - ALL of them
4. Shocks - all of them
5. Turbo - at least 2
6. Engine (block and head if possible)
The most complete things are, the easiest to swap. For example, I'd rather have a shock body with all control arms, brakes etc fully assembled so I can just mount the complete assembly instead of taking the whole thing apart. It all comes down to level of preparation and the risks you're willing to take.
Depending on the racing discipline, you can also bring spare body panels, windshields etc, but for grand touring I think there's relatively low risk for that. Also - the racing destination matters - if I was racing at Calabogie I could easily drive back home to pick some parts up if I forgot them. If I was driving to Vegas for a race, you better believe that truck would be packed to the top with spares (lesson learned)