Going from 8.6:1 to 10.5:1 will give good low end gains. Just remember that the compression increase comes from the piston design and has nothing to do with the oversized bore. Go with the minimum oversized piston that you can get away with.

 

the cam and higher comp will help but nothing to run with 400exs in a drag race. Get gregs 370 kit if you want some better power gains but if you go that way get a port job and bigger carb to get the most power out of it.