My brother had a 76 with 16's mounted with 225/50/16 tires on back, he had it lowered and it looked really good. His was a real narrow fender body like yours, here is a pic when he was stationed in Germany.
I'm sure he had to have some good adjustments so he will not have any issues with rubbing. I drove it once and did not notice any rubbing at all on back or front. So this is a example of what yours could look like, depending which way you want to go as far wheels is concern. Good luck!