FWIW, about 15 years ago I had to switch the case on my front D30 to go to 4.56 gears. I called ARB USA and they were pretty decent about selling me the bits to change it for what I thought was a reasonable price at the time. I forget what it actually cost and that was the "before times" so probably doesn't matter anyway. Give them a call and see.
Re: thick gears and more likely spacers, Spidey-sense says that such things do (did?) exist for high pinion Dana 30 axles but maybe I'm conflating the low pinion in the 2000-2001 and the TJ. I've been out of the Jeep thing for ~10 years and it's amazing what I've forgotten or mis-remember. Sometimes it's better to have no knowledge and research anew than second guess old, broken knowledge. Actually, on second thought, I probably had to go the route I did because HP30 spacers don't exist.