Not quite sure I understand the question. We've been racing Hemis for almost 50 years...still running Nostalgia SS with old school stuff, iron heads, cross ram, etc. 426 inches.

Not quite sure what you mean by how much they can 'take'? To give you an idea, we run iron heads, old TRW 12 to one pistons, and the cams we have used over the years have been a variety of rollers, Crane and Racer Brown, usually around .700 lift and 280-285 degrees duration. That was pretty much SOP during the day, and it hasn't changed much in a combo like ours. The SS/AH cars run over .800 lift, but there is a lot of other differences.

Don't know if this helps you or not, but I thought I'd chip in.