The rumor has been confirmed. It was a rumor to me, anyway, I don't know if anyone else had heard this. Headers for a 64-77 Chevelle will fit a first gen. Jimmy with a big block using small block motor mounts. The headers made specifically for our trucks don't work unless you use big block motor mounts, which will only fit 2wd vehicles. Summit graciously sent me some Hedman Headers PN 68190 after carefully noting my credit card number. The fit well and look nice; I'm a happy camper. 1970 GMC Jimmy 502HO/SM465/NP205 doesn't run just yet!