Go back to other thread and read the setup we have for a hardtop 68 Coronet 440 with a 318/904 and 2.76 gears. Milling is expensive and if you take too much off the heads you'll have to have special pushrods and you'll need to have the intake milled to port match the heads. Plus if you're pistons are down in the hole it won't matter because piston height is important in compression. Also, choosing the right cam is crucial for building cylinder pressure for your application.
Actually in a heavy car like his it depends on what he wants to do. If he puts larger valves in then he will loose on bottom end and gain on top end if he goes too big of course. Unless he has some 3.55s out back.