Hi
The two engins share the same starters,That being said there are two different starters for these engins.
One is a gear reduction starter,which should be whats on your truck,and should be on the 91 6.2,
the other is a bigger version of the regular starter used in the older GM gasser trucks.
If for some reasone the 91 is the older style non gear reduction make sure you get the braket that holds up the front of the starter,and the bolts.
Best if you buy some new bolts from GM of the proper length and torque to spec and retorque every oilchange
Parts to fix your starter are pretty cheep if you know anything about the insides of starters
Good Luck Thomas
90 Chev 3500 c/c 4x4,6.2na,400 auto,4:10 gears.DSG Timing gears,main girdle, isspro tach, pyro,boost,oil and trany temp.Dual Tstats, High volume peninsular pump,on shelf, Custom turbo and intercooler 85%complete. Change of plans for the dually, it's going to get a Cummins. Both trucks are Blue 90 4x4 crews