I thought GTAs with the 350 were not avail. as converts. (even from the factory because of CAFE ratings) because they started as carved up T-tops.
GTAs with factory T-tops could only get the 305.
The 350s were sent to ASC for conversion by the dealer. Only 305 GTAs were factory built ragtops (87 and up).
I think the same deal for Formulas.
Gotta check
www.thirdgen.org to be sure.