Would a frame from a 76 El Camino fit a 73 GMC Sprint. Thanks in advance

In a word, yes. The brakes were upgraded in 1976 due to federal requirements. Something you want to retain from the 1973 frame is the double hump crossmember (allows clearance for dual exhaust system). The double hump crossmember was discontinued for 1975 when it was retooled for clearance on the RHS for the new catalytic converter and single-only exhaust system.

Fergus eh? Nice little town. I haven't been through in a couple of years though. I'm originally from Ancaster. When I went to Ancaster High School in the late 70s there was a 1973 GMC Sprint that belonged to a secretary. It was silver with woodgrain sides. Wouldn't be yours now by any chance? (long shot)

Hi Cam and thanks.Any other body or mechanical parts interchangable.
Mine is Dark Red Metallic and is supposed to have the woodgrain but its long gone.
What part of TO.are you from.Grew up in Etobicoke and then Mississauga before moving to Fergie. Still work all over Toronto and surrounding areas.

Hey webb1, I'm in West Hill / Rouge River area. I just got back from the Eastender's car club meet. There are 1 or 2 Elky's from that generation in the club, plus I saw a very nice '76 Elky by my house 2 weeks ago.

As for interchangability between the 73 & 76, most everything will fit. The 1973 front end will only allow the 73 grill, but 1974-77 can swap grilles despite looking different from each other. Bumpers were the same from 73-75 up front, then 76 & 77 share a revised front bumper. Front bumper filler panels were done in 3 different versions: 1973 only, 1974-5, 1976-7. Out back all years of Elky (73-77) share the same 2.5 mph rear bumper that was sourced from the 1973 wagons. Speedometers read to 120 mph through 74, then went to 100 (with metric secondary scale to 160 km/h) from 75-77. Radios are the same (I think), except in 1977 they changed the style of numerals. 1977 was also the year that RHS mirrors (if used) went to the convex mirror (Objects In Mirror Are Closer Than They Appear.)
Let me know if you have specific questions and I will try to help if I can.