GMC much more heavy duty in a lot of ways. Even the grill was bolted directly to the top of the frame instead of the front sheet metal and you could actualy push with it if you weren't concerned with cosmetics. In the 55-59 trucks GMC had heavier everything including two diagonal tubes from the corners of the firewall to the front of the frame and in 67-72 GMC never did use the coil spring rear like chevy. After 73 as far as I can tell they are generic. Just a few of the many differences in the earlier trucks. When I look for stainless trim around windows and windshields for AD trucks I find a GMC and there it is.
