Ideally, you find a wheel & tire shop that can help you out with measuring and trial fitment. Two basically identical cars, particularly back in the day, can have significant variation yet still be within factory production tolerances.

Also, you have several variables involved. A really good measurement and trial fitting of the wheel and tire combo would be best. Initially everything might fit, then you turn the steering wheel and the tires rub. Or, you go over railroad tracks a little fast, and they rub. Or, everything seems to fit, except the leaf springs are in the way. If they are anywhere near standard design limits, Best to get a trial fit before you buy.

Beyond that, if you really want to go it alone and risk having to return things or worse, not be able to return custom-made wheels.... you could go on YouTube and/or Google the technique for measuring backspace and fenderwell contact points and try your best to figure it all out.