I'm going to reiterate what oilhammer and others have said: If you want a diesel generator, go buy a diesel generator unless you are dying to have a difficult and complicated project. Between the high cost of sourcing all the parts individually, figuring out the injection system so it runs at a constant speed under varying load (required to maintain 60hz), and the time and effort for all the fabrication, it won't be any cheaper than buying an existing unit. I paid $1000 for my 8kw Westerbeke with 3000hrs on it (still runs great). To be fair, in the Seattle area there's pretty much an endless stream of boat owners with far more money than time that replace their generators at the slightest hint of a problem, so these units pop up regularly on craigslist. Other places probably aren't quite as lucky, but eBay still has a decent assortment to choose from. And as much as I have respect for TDI's, they just don't compare to a true industrial duty diesel engine in ruggedness and durability (Yanmar, Kubota, Isuzu, Cummins, etc. . .) (the timing belt vs timing gears is one of many examples).
Unless you have a machine shop or some other large demand for electricity that would directly aid in your survival, or access to abundant crude oil or animal fat to use as fuel, a larger generator is a liability, not an asset. I'm still of the opinion the best option would be an air cooled single cylinder Yanmar driven generator. These engines are only a little more complex than a Briggs and Stratton, and you can buy Chinese clones for only a few hundred dollars (see Alibaba), so you could easily stock up on parts for cheap. Search for "MEP Yanmar" or "MEP generator" on eBay, and you should be able to easily snag what you need for $2000 or so (less if you are patient and willing to piece things together).
If you really want to see the thought experiment of "What would happen after the apocalypse", watch the second season of "The Colony". (The first season wasn't as good). At first, in order to get electricity for power tools, lights, and light welding, they hook an alternator to the pto of an old tractor. They rendered the fat from some pigs as fuel. Again, sourcing fuel was a major issue. (I would have drained the oil out of the abandoned cars, but that's neither here nor there). Eventually, they build a windmill using the front bearing hub off a car, some bicycle chain and sprockets, and an alternator. That worked very well for them.
I'm still of the opinion solar (or wind) is the way to go. You can buy panels for under $1/watt now, so 1kw is less than $1000. If you're handy with electrical circuits, you could probably feed the dc straight from the panels into the supply side of the charging circuit of a larger UPS (say 5kw), and that would act as your charge controller and inverter. That'd give you more than enough power to do some (intermittent) welding, power some lights, run a water pump (again, intermittently), and a refrigerator.