Alright, I feel like a DA! This is my 9 RX-7. I have had a lot of first gens and some 2nd gens. I even have a 90 that I popped a 351C under the hood in. I currently have the afore mentioned 90, and an 85 and an 80. The questions I have are concerning the 80 & 85. I have searched a lot of threads and am a little confussed. My 85 engine is locked. My 80 engine only has 72k on it and runs fine. The 85 is a 5speed while the 80 is an auto. The 80 is shot body and interior wise. So, i'm putting the 80 motor in the 85 body. I know about the exhaust differences but am confussed about the flywheel and balancing. Also, the 80 has a small er radiator and larger oil cooler than the 85. What is the easiest way to rebalance the engine for the fit into the 85? Any help would be appreciated.