My drivetrain / suspension is 99% stock. The exceptions are the tires and a fuel pump I haven't changed yet. I even have the cable brakes.
Assuming you have a pickup and you have 85 horsepower wheels, I see no reason why running radials would be a problem. To run without tubes I would clean and paint the inside of the rims. I was worried that air would leak past all those rivets holding the rims to the wheel centers, but that hasn't happened on me. As far as the tires themselves, I went to Discount Tires and looked at all the available 215-75-R16 tires they had in the lower price ranges (I did this while still a college student) and picked one with a decent looking side wall.