Personally, I do run a 30 front with 35s. I have run it for over three years and the PO did for 5 before that.
I am not known as a light footed person with the folks that have seen me on the trail. My 30 (stock not the XJ replacement) is aussie locked, stock inner shafts (because I haven't broke them yet), superior outers (broke those), C gussetted, 4.88 gears, unit bearings, Spicer BJs and wheel spacers (just added) and it has been holding up fine and is my DD. I will eventually have a 44 up front for piece of mind, but is it needed? I think 8 years of wheeling on the 30 would say that it is fine for what I do. Would I upgrade to a 60 front and 80 rear if I could, yes.
All that matters is what you are comfortable with... spending, wrenching on and what your pocket book allows. I have seen 37s and 38s on the dana 30 on the trail (never more than once, because I dont wheel with those people very often) but I am sure it is doable.
87 MJ Chief in pieces
Bought/Wheeled/Sold: 85 CJ, 79 FSJ, 05 LJ, 06 WK