Unless your willing to lower your compression ratio you will not be able to run pump gas.When you run a blower your exhaust gas temp is higher.Your effective compression ratio is going to be higher than 9.5 to 1 .At a 4.5 to 5 p.s.i. your engine may have 11:1 compression.I ran a 454 with oval port heads with a B&M 174 supercharger ,boat picked up about 10 m.p.h. in a 23' I/O.You also have to modify the carb & fuel system to prevent a lean condition.Ignition timing limited to 28 to 30 total.@ 100 H.P. gain also required a larger prop pitch.This all cost $$$$$!You may be better going with a set of Merlin Marine heads.They have 269 oval ports that flow well for about 1500 dollars.I like the blower power but it cost me twice as much as I thought it would be.As far as bottom end depends on cast or steel crank , rods , 4 bolt block? I hope this helps you ????