Need some tire recommendations and sizing for my son.

He got a 340 with it and bought another 340 for the duster he had to get rid of so he’s good engine wise. I have a set of Speedmaster heads that I have to finish for him that will be getting a 2.055 valve. He lives in the Denver Colorado area and works at a body shop.
Sounds like he is set! Wish I could find a 340 locally.... lol