TIRES TO FILL IN THE VOID ON 17" RIMS-my new tires suck

I would love to run 15s on the car a could get a lot of meat back there but I thought it might look funny with 17s in front I don't think 16s will even clear my rear calipers. I do appreciate all the comments Everyone has an opinion and the purist I applaud keeping the original, original. If everyone modernized them no one would no what they looked like. Sometimes I wish I would have kept the slant six. But when I'm running down the highway at 85 mph turning 2100rpm not so much. That's why I ask opinions here and not my friends everyone here generally has good points positive and negative.