I think that if I were to build a Corvair today, it would use a Porsche 911 Transaxle and a Subaru FJ20t from a WRX, or the FJ24t from the WRX STi. Dune buggy guys have adopted these flat 4's with great success, and I am sure I could solve the cooling issue with a little creative thinking. I would also swap out the suspension front and rear with something more modern, maybe FD RX-7 front. The rear I would have to think about.