....a few items....
Not to discourage you or anyone wanting to resin cast.....been doing it for 11 years.....almost a second hobby.
By the time you purchase the material to
PROPERLY cast tires, you could have purchased a few sets of tires....I have yet to cast one tire and have no desire to do so at this time....I probably will at some point in time.
Point is its less expensive to buy the parts or pieces that a vendor may have for sale than it is to try and do it your self. I cast what I need for my builds that are not available from anyone ,anywhere.
Not all vendors care whether or not they have the dimensions of their tires posted on their website , which is their financial loss as far as I am concerned. I recommend and have purchased tires from Big Donkey Resin
www.bigdonkeyresin.com Called and talked to Larry about a period correct build that I was doing....he was very helpful. Be sure to check out the gallery ....a lot of modified builds from the era that you are interested in are there with product information on the tires.
Before you start pouring rubber and resin , I would suggest giving this forum a visit.
https://alumilite.freeforums.net/board/4/molding-casting I'm over there as well, lots of helpful information plus Mike and Carol from Alumilite answer questions as well that are posted.