I used a ford 16" one on my stock steel rim on my spare tire and it fit fine,if thats any help...
I never tried a GM one on a ford rim,but I had a set of 16" ford rims on my '77 GMC 8 lug truck long ago,(around 1990 ford vintage rims) and they appeared to have the same mounting lips for the caps as the GM ones,so I'd guess they should work-(I didn't have and chevy caps to try on them)..I did have to use the ford lug nuts with the 1-1/16" hex and larger taper though..