[Mark Worthington]

I think you'd want to put some sort of an air-cooled Porsche engine in it - probably turbocharged. I also expect you'd pay dearly on a $/hp basis compared to a V8 - that ass-engine stuff is expensive. While a flat 12 like the originals had would be wonderful, it would either be outrageously expensive or it would be utterly unreliable, IMO. I've read that Porsche had to do a lot of development work on the 917 engine to get the crankshaft harmonics sorted out. Based on what I read, I think it would be nearly impossible for someone to "join" two 6-cylinder boxter engines in an effort to replicate the 917's mill.

If I could fit into and afford and race a 917 replica (I can't), I'd drop a worked Chevy LS1 into it. It's priceless to see how pissed off the Porsche diehards get when people show up with 911s that have Chevy engines in them.