That's kind of like asking how much does women turn you on. Well if your gay and the answer is not at all, then I suppose the question isn't difficult. However for the rest of us the obvious question is what type of women? Old, young, blond, fat, skinny, big tits, ugly, are all variables that matter.
A 383 & 400 cid Mopar has a shorter stroke than a 350 Chevy, but what does that prove?
There are two main areas of concern. Where does the rotating assembly fail? Where does the valves loose control - (typically before they float)?
If the valves float before the rotating assemblies failure point, you will break a valve spring before the bottom end grenades, assuming the rest of the valve train holds together.
The third area is a decent
oil system. If the
oil flow is too slow or not enough cooling, the
oil will break down and metal to metal contact will take the engine out. If the oil pumps up to the top of the engine faster than it can drain back down, you will run out of oil at sustained high rpms.
A stroked out big block can be built to turn high rpm, for enough money. It's not all that ridiculously hard to get to 7000. but it is a whole lot cheaper to stay under 6000. What bore and stroke, and what valves sizes can sway these numbers a 1000 rpm either way.
Personally I prefer to keep my small block under 6000 rpm. Don't really see any reason to limit a big block any lower. They just tend to live longer and fail less catastrophically at lower rpm.