I just switched from Carlisle ST 225/75R15C with a 50 PSI max to Maxxis ST 225/75R15D 65 PSI max. What PSI would you run these load D tires at. MY GVWR is 9015lbs.
I'm an expert on nothing...but here is the load chart for your tires. I'd run them close to max. That's what I do with our Maxxis. (I'm running LR E's) This will give you some margin.