short or long throw out bearing? please help!

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Hi all. so im putting my 72 swb 4x4 back together and i'm not sure about what throw out bearing to use. When I disassembled the truck and took the old clutch out I thought it had a short t.o.b but my friend just replaced his and it wouldn't work. turns out it needed a long t.o.b. This morning i went to o'rellys and got an off the shelf kit. and it came with a short one. but my buddy is telling me not to use it. what is true? any help would be good. I have a 98 vortec 350 and im using the flywheel from that engine. The kit i got is a 12 1/2 clutch kit for a 1972. By the way its a 72 swb 4x4 350 (vortec) and a sm465 and np 205. thanks.