With higher lift cams, always check valve guide top to valve spring retainer clearance. Dump the stock, tired springs and get fresh ones recommended by the cam grinder. If the heads and block are not milled, almost any flat tappet cam will darn near fit, piston to valve clearance wise. But always check it. My 69' 440-6 pac stocker motor, with pistons 0.029 in the hole, 0.021 gasket and milled heads to cc at 80, can handle "stocker" cams with 260ish at 0.050 duration. Its very tight, but it can fit. Its the duration that will smash the valves into the pistons.