The broad goal is to replicate the performance of the 300 HP Lycoming. So I'm looking for 300 or better @ 3000 RPM or less. In theory, the BMEP required is within the reach of current LS engine technology. This is why I'm driven to the biggest displacement I can get as it relaxes the BMEP requirement. A 427 "only" needs a BMEP of 185 to reach my goal, while that 500 inch monster would do it with 158. This is speaking of the final configuration, of course - the engine in this thread is just a learning exercise. concerning your last question, you're speaking of bell housing and front accessory holes between the LS series and the Chevy V6? Off the top of my head I don't think there is a 6 that shares the LS pattern. Even among the V8's, the LS has a unique pattern. It's close to the traditional SBC, but one hole is off. That said, the car guys will bolt the older transmissions up anyway.