Biggest rear tire on a C10

[JKady]

Wondering what the biggest/widest rear I can run on my '70 is before the frame starts to interfere? Basically want a pro-street look without having to rebuild the whole rear of the truck since it's my daily driver and I like how it drives. Planning on a drop to be decided after I get the tires and wheel package under the truck. I'm running 31x10.5 now and they've got a lot of room, but big big street tires aren't something I can just run down and grab from the local used tire guy so I would like to know what fits before I go dropping coin on new shoes.