According to Larry:
"And for the realists in the group, call Kennedy. Under $2500 total for
a
Subaru SVX flat six turning 230HP, do-it-yourself."

And for those interested in efficiency, those spark igniton motors get
up to about 25% fuel energy-to-work conversion at their best.  Typical
little diesels go 31%, but the amazing new VW TDI series runs up around
a world beating 40% max in stock form.  When modifing a total vehicle,
these might become important considerations for entering into your dream
mill.  While the best of those TDI motors aren't currently imported to
the American continent, at least by crossing the Canadian border and
settling for the little 4 cylinder version, you could visit a salvage
yard and obtain a genuinely efficient motor.  Getting a 5 cylinder 2.5
liter VW/Audi TDI from Europe is my dream for repowering a Vanagon
Westy. I feel the Subaru conversion might have a lot of appeal for those
who don't mind waste. 

Dreams are like success.  Don't let anybody define the word "success"
for you just as you should also decide what's best suited for your own
dream.
Blue