I ran some numbers using a tire calculator. 265/70/16 I think we'll be your closest in size (.04 inches shorter diameter), and it's a factory size for 3.92 geared trucks. 245/70/16 is factory for 3.55 geared trucks.
I'm running 245/75/16 (.18 inches shorter than yours) on my 3.55 geared Dakota. I like it. And it's a common size for box trucks and delivery vans. So there are lots of options for tires, and many in LT sizes.
I've tried 265/75/16. They're a full inch taller than yours. They were fine most of the time, but I got some rubbing at full steering luck. Many say they are fine if you have a lift, and most agree that it's the biggest size that will fit in the spare tire spot under the trucks (I never tried).
This is the info i was looking for. Thank you. I didnt want to go too big, and have them rub like when i put 31's on my stock 95 Dakota.
We have a couple shops around where i live that sell nearly new tires, and 245/70/16 and 245/75/16 are sizes they have dozens of. Before anyone starts the whole, never buy used tires thing, what these shops do is work with the new, or fairly new, car dealers, and buy the good (they cant have any patches or plugs) tires the dealers removes from new cars. Where i live, if a car dealer replaces a tire, say for example a customer wants a specific brand of tires, or something more or less aggressive when they buy a car, the dealers arent allowed around here to resell the tires they removed, or put them on another vehicle, so they sell them to wholesalers, who are allowed to sell them to the public. The last time i got 31's that way, it cost me over $350 a pair, but, i can do 4 245/70/16's Armstrong Tru-Trac's (kind of the size i was leaning towards anyway), for $300 mounted and balanced, and 16" 6 lug Dakota/Durango wheels around here go for $15-$20 each, so, to swap to 16's, will cost me, at least the first time, not much more than a pair of 31's will. Unless you go through a wholesaler here, tires are astronomical, even before the environmental, recycling, and other fees. Those same Armstrong's at Walmart here, mounted and balanced, after all the fees and taxes, come to more than twice as much as a wholesaler.