You can have the valves ground down to get them to sit in the seats a little further or buy or rent the tools needed to cut the piston valve reliefs deeper.
Are you checking all eight cylinders for P to V clearances? If not do that now before finding out later that you should have twocents
I raced several different NHRA legal 1963 426 M. W. motors, both 415 and 425 HP and the stock rods are not all the exact same length, same as any Mopar OEM rod sets from the factory scope
My last 425 HP short block had .009 difference in rod lengths puke scope Same thing on rocker arm ratio,, they are not all the same shruggy
Good luck, take the time now to get all parts to fit correctly up
I have ran the intake to piston valve clearances as close as .029 on my original 415 HP short block due to having the heads cut to reduce the CC from 86.0 CC + to 81.5 CC based on checking ONLY one chamber in each head and not rechecking the P to V clearances realcrazy I got lucky on that on, not so on other parts changing without doing all the clearance checking whiney
Never ASSUME anything on any motors, ever twocents

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)