8 3/4 question

IMHO: they all work well as anything will fail regardless of case of number if you beat the snot out of it.
If you have a large hp / tq engine the 489 or 742 is more desirable. If you run a stock or street modified engine and drive like normal. All 3 will last as long as they can. All parts eventually wear out. Most of these pumpkins are 50 years old now.
I’d take a 741 case any day over say a 7-1/4 rear behind my 340.