Wheel size for 76 duster

Hey Fabo members got a quick and hopefully easy question for everyone. I'm a young gun who owns a 76 plymouth duster with a 225 slant six 4 speed with 5 on 4.5 bolt pattern disc up front and drums in the back. I have the stock axle which is a 7 1/4 I believe. I'm in the market for some new wheels and tires cuz mine are shot. I plan on converting to a 8 3/4 rear end hopefully this fall but by next summer for sure. Wheel size and tire combo are much appreciated sorry in advance if throughout this thread I ask stupid obvious questions.