Hi fish n fool,
Think we have the same fiver which have 7K axles and mine has GVWR of 15,000 lbs.
I too am getting ready to replace my tires as they're still OE ST Duro's and 7 yrs old. Guess I've been lucky. I posted same question not long ago here and the Carriage forum and based on the responses plus my own research I've decided to go with GY G614. Any ST tire for these heavyweight fivers are too borderline and often too little or zero reserve for load capacity. I may need to replace wheels as I'm not sure if mine are rated for 110 psi. If I had the extra $$ I'd seriously consider upgrading wheels to 17.5 which then give you more tire selections.