The distributors will interchange with Chevy distributors as long as the gears match the cam. So the later GM HEI modified for a Chevy can be used in a GMC.

I have run a Pertronix in my 248 for a bunch of miles.

"It's just a phase. He'll grow out of it." Mama, 1964

1956 Chevy 1/2-ton 3100
1953 Chevy 6100 "The Yard dog"
1954 GMC Suburban Now with a new proud owner.