If you are looking for aftermarket rims for GTs, check out
Vintage,Track & Overland = VTO Performance, they have several styles of rims in many different sizes from 10 inchers on up in standard and alot of oddball bolt patterns, backspacings, offsets ect. They have a few to chose from in 4X100 for the GTs. Ive used them before for British cars (MG, Triumph) and im a big fan of thier Panasport look alikes, the "Superlites". Good rims and prices are reasonable. Should be able to find what you may want on there. Hope this helps somebody