If you mean stock like the original BFGs or Firestones or Goodyears those tires haven't been made for 25+ years. If you mean the original size tires any tractor/lawn mower supply store like Tractor Supply Company will have them or can get them. They still are common size tires used today they just have different manufacturers. Roger
Again you can buy those tires many places. I know I have bought both of those sizes from www.tuckertire.com. That will send you to their E-Bay store so you can see what they have. I just generally call them on their 800 number. Prices are good and they are as cheap or cheaper on shipping as anyone. Roger
Is that first photo a rear tire? I'm not familiar with the size indicated. But I seem to recall from your thread when you first got the tractor, that you have narrow rear rims?
At any rate, the fact you have the narrows on the front and back, is consistent with GT-1 and GT-2. (GT-4 was narrow front, wide rear).
So then the only question is which tread design, "Traction" or "All-Purpose"? I don't know enough about the tread patterns to comment. But you might call Miller tire and ask them -- I have a feeling they will know.
My '66 came (to me) with narrows on the front, and wide ("floatation", i.e. 23x8.50-12) on the back, sort of hybrid of GT-1/2 and GT-3. (I guess if it had studded fronts, it would be GT-4.) But that's not how it came originally. Mine is supposed to be a GT-2 narrow wheel/tire set (as indicated by the tractor serial number). I'm bummed that the narrow rears got separated from the tractor at some point. You still have narrow rears which is very nice. Don't part with them.