i need help w/duster engine

Guitar, There are other ways as noted. However, not knowing where the existing cam is in relation to the piston, yes, I say check from 100° to 100°. Same reason when I degree I go .050 down the lobe. Really only a few degrees would work but the idea is to be sure.

Big... The valves are closest just away from TDC. You have to keep the dynamic relationship of the parts in mind when you think about it.

Mel, the heads flow 266, they have the potential for about twice that when matched properly. If you're making 496 you're basically there. If you had the lifter bores bushed any lifter assembly should work fine but they may not clear the bosses in the valley area. Grinding on a complete engine is not a good idea. But at this point I dont think you care. If the season's over... why are you rushing again? Dont forget you will need the right valve springs which will require valve spring seat work in order to use the springs the roller cam needs. Plus, you will should really replace the valves if they are not stainless as the roller cam will hammer the heads off stock type ones.