I run the "Power King" LT bias-ply that many places run on their smaller delivery trucks. The good thing about them, they are rated at a higher speed (where trailer tires are rated at 65mph). I inflate them to the max (65psi) based on the rating and they never get real hot even in the middle of summer running 70mph. Now, I will be the first to say, run them at a lower pressure and the will heat-up a little (you can feel the temp difference between 62 and 65psi). In fact, since the trailer rides at an every so slight pitch down in the front (when water tank is full) on the 1966
Overlander, you can feel a slight difference in the temp from the front tires to to the back ones that have a little less pressure on them.
I will say, this setup works best for me since I also pull with a 1962
Galaxie Conv. and a 1968
International Travelall. If memory serves me right, I have the hitch head setup to where I need to hook-up to the 7th chain link on the load bars when pulling with the Galaxie/Travelall to bring the tailend up on the car and the front end of the trailer. When I'm pulling with the Excursion/F250SD, I only need to connect to the 2nd chain link on the level bars since the Fords can handle the tongue weight of about 450lbs (no water in fresh tank) and thus the reason why I normally run with a full water tank when pulling with the Fords to give it a slightly better ride though I run empty when pulling with the Vintage tows.
Again, not saying I'm right just what has worked well for me over the past ten+ years with Vintage and Heavy Duty tow rigs.