engine swapping

What's the difference between a chevy 3.1 L like out of a 91 lumina and a pontiac 3100 out of a 96 grand prix. Both have the same fuel system. The chevy say's 3.1 on the plenum and the pontiac says 3100. Will the cyc. head's interchange?

I hear from a guy that they are the same. Duno if i can take his word or not. I'd rather hear from the forum about it. Tks Scott

Head's won't interchange according to hollinger