Wow, a lot of people seem to be speaking up about why it's bad for Jon to change anything on this car from stock (should he even withhold the ventectomy?). Having been in this car and having seen the condition it's in, there won't be much "original" left. That value is gone. Frankly, it's a 12 year old B5 Passat with 140k that has seen better days (to say the least). It's only cool factor is the fact that it has the AHH engine and the one-off transmission that mates to it, oh, and that stubby passenger mirror. To get this thing back in running condition is going to take a lot of work. The interior is done, gone, kaput. The body is, well, it's still together (mostly, and who knows what has or hasn't been replaced already), but it's not pretty (take a look at the pictures of the back left fender). The actual value in "originality" of the car is completely lost, except perhaps as a rotting piece in the fictional VW of America Museum, or as a bondo special.
I realize that to a surprising number of you I may be speaking heresy when I say that as "neat" as it would be to have an original and stock vehicle in mint condition, this just isn't a realistic ... or even worthwhile example. Beyond that, it's not as if this is 1 of 2 in the world. It was a production piece in Europe. When rehabilitating a car, there are two frames of mind, stock, and custom. Well, Jon is a little closer to the custom side and it's his car (my dad is a stock Corvair guy). But hey, even one of our trusted TDI mechanics said he'd have just dropped the engine and drivetrain into one of his vehicles. So perhaps we should be thankful that Jon 1: likes the B5 Sedan, 2: Likes the Emerald Green (can't say it's my idea of great, and it really could use a paint job), and 3: is extremely thorough in his research. Who blames Jon for not liking the tan interior? I have it on my 2000 Golf and it's nasty. Somehow that tan color makes everything show up, and there's no way of cleaning it. That whole interior needs to go (with few exceptions), so if he wants the leather GLX interior, I say go for it; VW should have done it.
Frankly, I think it's awesome that Jon is documenting a small portion of his research (and trust me, I know how small this portion is, I have miles of chat logs and links already), and the last thing I want to do is have Jon get discouraged about bringing this car some glory in a community of people who can actually appreciate the vehicle (unlike the previous owners as is quite obvious from its current state).
So please, as much as you want to beg him not to do something for the sake of maintaining "original" or "stock", just consider it a bonus that this car didn't end up in the crusher or dismembered or otherwise.
Now, if this were my project, I sure as hell would love some research help (does anyone have ETKA access for part number cross referencing?) and to tap the vast storehouse of knowledge in this community to deal with the immensely frustrating task of trying to find--let alone get--the right parts, and to keep whatever mods Jon does decide to do from blowing up that engine.