In the UK, small diesel automotive engines are everywhere - Peugeots, Citreons, Renaults. Also, Ford have made Diesel Ford Fiestas for decades - and older models can be had for next to nothing :). Getting a diesel engine over here for transplant is very cheap and easy!

I've had ideas of a dual-fuel system, with a small 2-cylinder engine, mounted somewhere in the rear of the car, running on SVO/WVO, for long range cruising - the idea would be to make it as light as possible, and then have a very powerful petrol engine for the grin factor!

That last "tank" wasn't a full tank. I needed some petroleum diesel to thin out the biodiesel already in the tank in preparation for some much (more typical) colder overnight temperatures. The 70+ is an anomaly that will be averaged out eventually.
This is actually my fourth Passat diesel. The other three came with the TDI engine. This used replacement with the VR6 was about 1/2 the purchase cost of a used TDI. I pulled the drive line from the third one I had repurchased following an insurance total loss and dropped the diesel bits into the emptied engine bay.
There is a bit of a time line on Fred's www.tdiclub.com in the 'forum' under the 'conversions' heading. Use my screen name (same here and there) as a search key to winnow out the others, or don't to see how they are progressing with their transplants.