Yep, just strength. Thinking of going 37's next time around. Currently I'm running 35's, with 4.7's in the case with no issue (also wheel spacers). But later may be going 37's and a Dual Ultimate setup. Can a stock rear axle shaft hold up to that kind of torque? Would like to keep it Toyota, not a D-60 or anything.

85 4Runner - With NEW Marlin 4.7 Gears!! It's a whole new beast!