Sorry to hear you are having issues. I have slid my SM420 under the truck and then with a cherry picker also thru the passenger door, thru the hole in the floor, pick up the gearbox and push it right into place and bolted it to the motor. Are you connecting a closed or open driveline to the gearbox? Is your gearbox on the floor, waiting to be picked up? or are you trying to lower it down thru the hole in the floor?
Craig
My '50 Chevy 3100 5 window, '62-235cu, 3:55 rear
My truck ....... Respect The Rust
If I'm not working on my truck, '65 m00stang or VW camper, I'm fishing with the wife or smoking Salmon.