How much should it cost to rebuild 741 sure grip

I think the 741 case will be fine. Regardless, first, you need to see if the carrier you have is even rebuildable. If it is the cone type sure grip like an Auburn, it is not. The clutch style however is. Usually you can score a new set of clutches and steels for under 100 bucks new. They are really quite simple to rebuild. You should try it yourself and save the money if it's a clutch unit.