would 225/55/15's fit on our cars.. I think my brothers 3000gt stock rims are lighter than mine (89 GXL).

Also Ived searched high and low for the answer, has anyone scaled 89 GXL rims? Im guessing there pretty heavy.

 

There are a couple of threads that cover the weights of all the Fc wheels, in this section.

225/50/15 fit on the stock FC 15x6 and 15x6.5 inch wheels with their 40mm offset.

You would need to know the size, offset of the 3000GT wheels, as well as the bolt pattern to see if they would fit on a FC.