Let's break down the steam hole question.
We know we bore/hone 400's with torque plates mainly because the design of the 400's bores move around alot.
We know the 400's where never designed for high performance use.They where never intended for high compression use.I.E.:76cc heads
We are very sure with increased output=increased heat.
Now I worked at the Chevy engine plant as a engine tester when the 400's where new.Also my racing operation over the yrs in 9.90 cars of 17 last count cars used 7 400's of various size.All of them with steam holes drilled.
We know mainly because of the well documented issues the OEM 400 blocks have is the reasons why the aftermarket blocks where designed as they are.
The summation of this is if not for the leakdown sealing issues the 400's have,there isn't a sound reason not to have the steam holes drilled.
As a side comment.Any suggestion not to drill those holes is confusing as the reason.Or to run bypass hoses.At best that is very dated.At the worst it is to draw attention to themselves knowing it is argumentative post.Certainty drilling the steam holes is a proven preventive method.
If your asking which cam type would be the king of the hill given your SCR,a roller solid lifter with a rev kit is the way to go as long as you don't mind setting the valves.Certainly you have to have the springs for it and check the clearances.