I would definately go with the 38s because of the 16" rim.

Evan/wwwthreads_images/icons/crazy.gif
Contagious Off-Road

 

I've had a set of the 42's and they are true 42's. Great tire offroad-not a hi mileage tire on the road-that's for sure. I've got a spare (new) 42 if you go with that size

 

I'd go for the 38's myself. That's still a lot of tire, and most trucks (even with totally stock engines) can take full advantage of the benefit of this size. BTW, don't expect them to get much taller. 38's are really 37's - which means they measure 36. When I say they're really 37's, I mean that if you had bought that EXACT tire 15 years ago, it would have been STAMPED 13/37. That used to be Interco's largest size. Then they came out with the 42, and started filling in the gaps. Changing the stamp of the 37 to 38 was a marketing move done so the 36 & 37 wouldn't cannabalize each other's sales. In reality, there's less than 3/4" difference between the two. And 13X37 is actually a simpler way of describing "R85" - the size you'll find stamped on the largest Buckshot Mudder.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing

 

If your not sure about any tires fitting, go here: http://www.natltire.com/pages/fithit.html there is a tire fitting guide, they have a chart
that will tell you what fits with what lift for what model truck, its perfect.

 

Thanks for the replys.I think I'll go with the 13/38x16. I like the extra heighth of the 15/39.5x16.5 but don't think I need that wide of a tire, and also concerned about the tires coming off the bead when I dont want them to.Also thought about grinding down the calipers to fit 15 inch rims but that's probably not the best idea. Also the 38's are cheaper.