Thank God they limit the top speed to 257.9 mph! I'd be tempted to go really crazy otherwise. I'm guessing that any engine that puts out 1,000 hp is going to be temperamental, in need of regular tuning, etc. I'd be much happier with the same body and some variant of Audi's Le Mans diesel engine, perhaps a mere 300 hp.
Perhaps a V-8 version of Audi's V12. With the same piston and crank dimensions would yield 3.67 liters. Plenty enough.
**EDIT** Audi already had such variants. DOH!!!
http://en.wikipedia.org/wiki/Audi_R10_TDI