I'm debating on these two different sizes. If I get the 38.5s I'll have to do some more trimming and probably get the Gorilla warflares. I think the 37s would fit cozy with the 2"bl and 5.5" lift. But I sure like the idea of 38s. I'm hoping the d44 with warn axles and ctms will hold up to either of the two. The rear 9" will have 31 spline axles---I know I'm pushing my luck with both tire sizes. The motor is a 302, trans is a c-4 and the gears are 4.88. BTW, this is for my 74 bronco. I will be driving it on the street some but mostly it will ride on the trailer if going over 30-40 miles. I'll probably be purchasing these sometime in late January or early February.