I'm running D rated BFG muds as summer tires, 315/75R16's... Never had issues with a D rated tire vs an E, most of them in bigger sizes have very comparable load ratings.
Personally I'd suggest running 16's, tires and rims are both cheaper.
16.5's, well, they're getting to be dinosaurs, tire availability is getting slim, and decent tires for them aren't cheap.