Another option for the LS route, is the later L33 5.3 engines. They are still around 330bhp, and often they can be bought in the US for less than $1000. Although some accessories are in odd places ( weird water pump )

It would cost a little extra to rectify these bits. But unless someone was buying a load and importing them, you're still talking a few grand by the time it gets here.

For the Audi V8/rwd

http://www.locostbuilders.co.uk/view...php?tid=123404

http://www.pistonheads.co.uk/GASSING...+an+Audi+V8%3F

So if the engine can be sourced, it would still be a very viable budget option.

Thor in the UK or perhaps some of the Aussies will no doubt offer a bellhousing for the LS400 engine, often for the R-154 Toyota 5 speed, although these are getting pricey if you can find one. Still a very good budget option as buying a complete car with an LS400 in it will cost very little. And as with all Toyotas of that era, the engineering in them is outstanding.