Thick gears will be marked with a T after the serial number stamped on the ring gear. The dana 44 carrier has a carrier break at 3.73 / 3.92 gears. So, there is two dana 44 carriers, one carrier that fits 3.73 and numerically lower gears, and one for 3.92 and numerically higher gears.
Thick gears, were designed to offer the 3.92 and numerically higher gears, on the 3.73 and numerically lower carrier.
For example: I had a set of Dana 44 axles from a Scout. They originally had 3.07 gears. which means that both axles have the Dana 44 3.73 and numerically lower gear carriers. I wanted to regear to 4.88's, so I had a choice of buying the new 3.92 and numerically higher carriers and the standard 4.88 gears. After some research, I found 4.88 Thick gears. (488T) which would give me the ratio i wanted, and would still fit on the 3.73 and numerically lower carriers. I also did this because I think that a thicker ring gear will help in building the breakage out of the ring gear by offering a bit more stregth due to a thicker ring. (more metal is good right?)
Other ratios are available as well, 4.88, 4.56, 4.10 and I think even 5.13 can all come in thick gearsets to fit the numerically lower carriers. I purchased mine from Randy's Ring and pinion, (ringpinion.com) They were made by Yukon.
The Waggy carriers, other than spline counts, should not vary in size or from year to year. A dana 44 carrier is a dana 44 carrier, with some some exceptions being, rubi 44's, High pinion 44's, lockers and the carriers break sizes. The way to tell the difference between the carrier types (373 minus and 392 plus) is the thickness of the ring gear mounting flange. I dont know the measurements off hand, but I know they can be found online.
I hope this helps