Brian --
If anyone has a used Trac-Lok that old, it would probably have been removed because it wore out. They can be rebuilt, but the guy who owns Drive Train Direct told me years ago that the rebuilds don't usually last as long as a new unit. For a Dana 35, the rebuild kit costs about $65 and the new unit is about $225. For the difference in price, I'd prefer to have the new unit that's ready to drop in and will (hopefully) last longer.
Is your employee certain the '84 has a Dana 44? I didn't think they started using the D44 until model year 1987. I know for a fact that the heavy duty axle in the '86 MJ was an AMC Model 20. There is no mention of a Dana 44 heavy duty axle in the '86 factory service manual.
I'd suggest your guy call Drive Train Direct. I no longer have the phone number, but they're on the Internet at www.drivetraindirect.com. He can probably buy new units from them for less than what DaimstoreChrysler charges your parts department.