with my build my axle choices have changed a lot. at the begining i was going to build up my D30 and 8.25 to run 35's and then realised I'll want to go bigger later on so I decided for a HP D44 front and a D60 rear. then as my build progressed I decided that I might as well put a 60 in the front, so I bought one for $120 without axleshafts and thats what is going under the xj. Recently I decided to go with a 14bolt in the rear due to the pure strength in stock form, the 30 spline axle shafts are massive compared to the D60, the 14bolt splines are cut at 37* degrees compared to 30*deg D60 shafts, this is another strength increase.
for 38" tires yes i would say go with 60's, your d44 baljoints will see a lot of stress on big tires, not to mention a rear 60 will be full floating axle. Or you could go with a 14bolt in the rear.
I have a spare D60 rear for sale out of an 85 dodge truck sitting in my garage. its 65" WMS-WMS full floating axle. i'm not using it because I went with a 14bolt which is 67" WMS-WMS and sits under my XJ better with my 4.25`BS rims.