Tire sizes

[Pickle]

I have a 75' c20 and I need new tires. I bought 16 inch rims that are 8 inch wide and have been getting mixed answers from local tire shops. Some say that P rated tires will work fine, just not with a large load. Some say that it is illegal to run less than an 8ply rated tire on a 3/4 ton truck. Most that say I cannot go to a P rated tire are suggesting a 265/75 tire but I wasn't sure if that would give me any issues as far as turn radius and brakes. Right now not including lack of tread I am running 29x9.5x16.5 tires. The price difference between the 245/75 or 245/70 tires and LT265/75 tires are quite significant and if I can get away with the smaller tires would make my life a lot easier. I only have one 600 mile trip with a light load (my bed, dresser and a few boxes. i might possibly haul a small rented trailer) and then it will be city driving for quite a while. Would it be okay to stick with the smaller tires and just get what I can out of them and buy new tires after I move? Or would it be too dangerous and more worth it to get the bigger 8-10 ply rated tires and pay the extra $200?