need axle ratio and tire size chart
It's not quite that easy. Tire selection is influenced by the intended use of the car as well as what is available. Suggest looking at wheel/tire combinations fitted at the factory first. Convert to metric sizes. The rims that are on the car will dictate what can be fitted on them. If you're not satisfied, look for wheels and tires that are more in line with your tastes and will fit on the car. The wheels on 72 and earlier disk brake cars and all drum brake A-bodies used a 4-inch bolt circle. 73 and later disk brake A-bodies used a 4½-inch bolt circle. This was used by most other Mopars, FoMoCo, and AMC vehicles. There are a lot more wheel options for the 4½-inch bolt pattern cars.
I have an Excel spreadsheet where you input tire section width, aspect ratio, and wheel diameter. You also input the rear end ratio. It will give you revs per mile as well as rpm @ 60 & 70 mph. I played with the variables til I came up with a combination I could live with (235/60-15, 3.55:1)
What the spreadsheet won't do is tell you if it will fit your application. The wheel/tire combination might rub the inside of the fender or rub on the rear springs. It also assumes zero tire deflection (load), and does not account for slippage in the driveline.
If you're interested, PM me with an e-mail address where I can send the spreadsheet.
As far as the rear gear goes, figure out what you have. Usually, there is a tag on one of the bolts in the differential housing that has the ratio stamped into it. There are lots of options for getting the gear ratio you want/need.