some parts interchange between Chev and GMC, but there are definite differences too that prevent interchanging some parts .... a fleetside bed from 58 or 9 would fit [no such animal for 57], just need to make your own mount holes in the frame, BUT a short anything is a 3100, the 3200 is the long frame, sell the 58 emblems and find the correct 57 ones
Bill
