You could do as I do, I run 245-75-16's on the front axel, and 215-85-16's on the rear. I replace the fronts as needed, rears as a set ie all 4 as needed. Need to get 4 for the rear right now, trying to decide on M55's again, at 1200, or Coopers at 800! Or firestone HT's at about 600-650 IRRC. Then again, I have gotten 80K outo f the m55's, just not sure if I will keep this truck or my c2500 in the next few months.......so there we go!
I do the same with my navistar, tractions in the rear replaced as a group of 4, and the fronts are hwy treads......granted the K3500 is a 4wd.....I do run 245-70-19.5 in the front of the IHC, and had 8r19.5's in the rear, but last set went with LR G 225-70-19.5s, as they will carry one heck of a lot more than the 8rs would. 245's were too wide for the rims.
If you have 235-85-16's, you could put a 265-75 up front, and 235's on the rear. I find the 75's seem to last up front longer than when I ran 85's.
Marty