I guessing you have 700X15 tires on there now. Thats what was on my 1977/31' A/S. I asked the same question you asked & got two options in most replies. You can go with radials or stay with bais ply tires. If your wheels are too old, you may not be able to mount radials on them. You would have to buy new wheels. I had already put new wheels on, so could put either on. Most people recommended Goodyear Merathon tires if you go with radials. I decided to stay with bais ply tires. One reason was the radial tires will let the TT set about a inch lower & my TT is already about a inch too low. I can't let the hitch down any further & don't want to buy another ball mount hitch. I had very good service from my last bais ply tires & have no reason to change to radial. I went to schwab tires when in Bend OR & got their bais ply( 8 ply )tires mounted, balanced & out the door for $300. I've traveled about 4/5 thousand miles & they seem fine. I think either way is fine. I have two friends that have had Goodyear Merathon tires blow out. That afected my decission also.
SF CA area