Hi Glen,

tyre rating can be tricky, especially if you're going to be airing-down for the soft stuff.

On my BFG's the max rating is achieved at 80psi, so if you're planning to run lower pressures in the soft stuff you won't wont to be running a tyre that just exceeds your max-axle load.

See Load Index & Speed Symbol - Info - Bob Jane T-Marts

I'm running BFG's which are 126Q Load E rated.

BTW, how are the 315-75 16s wearing on the 7" rims. I know it is not recommended but I've seen a few comments where people say that you can get away with it. I'd be inclined to get those tyres re-fitted to your new rims while you are doing your suspension adjustments, then step up from there once things become clearer regarding rubbing/looks/etc.