Just a warning on the Pump Dusse engine. Camshaft problems! That's the BRM engine.
Also, all that VW stuff is very big and heavy with lots of piping, valves, etcetera. My ideal engine swap would be the soon to be released Ford 3 cylinder. It is supposed to be an entry market high volume engine (at least in Europe) so they should be crashing them soon. The electronics would be near impossible I guess. Too bad there isn't an open-source movement there!
By the way, don't you think that a diesel might shake the dash out onto your lap? VW is using a dual mass flywheel to cut vibration. It's basically two disks joined by very strong springs. Those springs break and then it's $500 and a very difficult transmission pull to fix.
Volkswagen is misnamed. It should be Corporatewagen- as in very difficult to fix yourself and gold-plated dealer prices.