I know this is an older thread but for anyone else looking for a drivetrain specialist check out KM Driveline
in East Williamsburg, Brooklyn.
They've usually got 260, 297, 760, 1310, 1330, 1350, 1410 and hybrid ujoints on the shelf; all kinds of yokes and ujoint u-bolts/straps, they do custom driveshafts with or without a slip yoke; they'll install SYE's; install gears, lockers, shafts, etc.
I've picked up a few ujoints and had them do my D30 gears and locker install. Prices are good and the work happens fast. For the gears/locker, I made an appt, dropped off the jeep @ 8am, picked it up @ 5pm.
Im not affiliated, just psyched to find a good local shop for this stuff.