I just went through this nightmare I also have. Fabtech 7.5" long travel lift kit that use those very same bushings 4wheel parts was able to order them
I have a 94 suburban that was swapped to vortec engine I'm running the 395 cam ls6 springs 1.6 roller rockers 411 pcm swap 60 over pistons mpfi injectors cold air intake and headers and true dual exhaust my truck is 6500 pounds with 35" tires and 9" lift 410 gears it has alot of power and I...
The nss hardly ever goes out check the shift cable and make sure it's going all the way forward are adjust the switch with the 2 bolts on side of trans if you have someone who can tune (hp tuners) they can just tune it out
If you have the ability rebuild it and add a couple of upgrades I rebuild these transmissions all the time and I love them with just a couple mods they will last a long time and parts are fairly cheap for them u could easily spend less than 200$ rebuilding yourself
Sounds like torque converter is on its way out it doesn't happen often I have owned 7 of these trucks with milage from 80k to 500k and it's only happen once but it sounds like what your going thru it started off ass light clicking and delayed engagement then one day no more forward or reverse...
Lots of fab work I have swapped a variety of seats and none of them will bolt right up 94-99 99-03 03-07 none without fab work and a couple new holes in the floor