when I mocked up an actual eagle head and early short block and standard head gasket it came out to around 11.5 compression. With the fast burn chambers, double quench pads, EFI, dual spark plugs, plastic intake... I would bet you would be totally fine on premium pump fuel. The only problem you might run into is if your tuner gets too agressive with the timing, these things really don't need much. Heck the apache is 10.9 and you know the factory is going to be very conservative on compression for emmisions reasons (NOX specifically). I think a low buget early 5.7 short block with a 6.1 cam and eagle heads/intake would be a buget motor to be reckoned with.