How do you deal with the different pulley belts size..???

I have a 261 with the small belt size damper pulley.... I shortened the water pump shaft and replace the original 1958 deep dish pump pulley with an after market... Trans Dapt only 2 3/4 deep now the pulleys line up...BUT... the size and profile of the damper pulley is bigger than the Trans Dapt water pump pulley... off hand I would say the original damper oulley is cut for a wide shallow 1/2 inch belt and the pump pulley is cut deep and narrow for something like a 3/8 belt.... will I have a slipping belt?? or will the...if I go back to the deep original pulley I will have to move the rad forward for clearance ....will belt life be affected..? or jump off at high revs...???

Bob C.

Bob C.
CMP Heaven
The Hammond Barn