www.fordsix.com/forums theres a few turbo 300's there and enough turbo knowladge to set the engine up correctly.. you can run all the way to 9:1 on average and still run some boost ( 4-5 PSI at that comp ).. my 200 I6 Ford is set up for 8.8:1 and to run the boost at 8 PSI, which for the 200/250 8.8:1 is considered the optimal comp ratio for a boosted street engine