You couldn't find any info because it doesn't exist. There's no such thing as a Gladiator J100. The later Jeep trucks dropped the Gladiator name and used the J10 and J20 designation (half and 3/4 ton). If it's a 74-86 version it's probably a J10, which has Dana 44 front and usually Dana 44 rears, but some 80's versions used an AMC20 rear. Not the same AMC20 used in CJ's, the J-truck version has one piece axles and a stronger housing. 74-79 will be Dana 44's with a passenger's side front offset. The rears may be offset if they came with the Quadratrac case. All J-truck axles are extremely wide for use in a YJ, around 67" wide at the WMS.
If it's a 73 or earlier model you don't want the axles, they are closed knuckle fronts and not worth the swap.
No J-truck ever used a bolt patter that is the same as a YJ, by the way. If they're 74 and newer they will be 6-lug. 73 and earlier would be 5x5.5", same as CJ's.
By the way, there was a J100, but it wasn't a Gladiator truck. It was a panel delivery truck, which was essentially a 2 door Wagoneer with no side windows and a barn door rear door. They are very rare and it's highly doubtful that this is what your buddy has.