Oops, I was thinking the '83 had a P90. That would actually make it the same as mine. I have a P79/F54. Without shaving the P79, the CR is only like 8.3:1. People get worried about the N47/F54 combo, but it's fine. Less than 10:1 in the Eastern states is no big deal. Out West, the max octane rating is only 91, so they have a bit tougher time running that setup, I guess. Mine runs great with zero problems. I paid $150 to shave the P79 and it is a sweet engine. It pulls strong to 7,000 and makes about 170 - 180 hp at the wheels. I haven't dyno'd mine, but a friend with nearly the same exact motor got 178 at the wheels with his. My cam is a bit bigger, but he did some mild porting. I'm guessing they ended up about the same.