At least on a lift you can get to everything and not have to crawl around on a creeper...or worse yet.............IN THE DIRT
The last rear main I had to do I said noooooooooooooo waaaaaay to the bottom up and yanked the engine out, steam cleaned it well and then went after the beast.
Discovered a weeping freeze plug under one motor mount (Sooooo...that was where the coolant had been going)
Installed a fresh set of freeze plugs and the new rear main seal.....in fact if memory serves me we rolled in new bearings while the bottom was off and dropped in a fresh oil pump too.
The timing cover seal was not stellar so ripped it off and stuffed in a fresh seal and a fresh chain while the cover was off.
The valve covers were a bit oily so removed the fuel injector lines and resealed the covers.
While it was right there it got a fresh set of glow plugs and took the injectors in for a refresh.
Just about everything that is nasty to work on in the chassis was given attention.
Thought about doing head gaskets but the engine did not have all that many miles...maybe 100K at the time.
Ahh well...that truck lasted us 300K miles 1986 K2500 Burb 4x4
Bought it with 30K on it from a dentist who's missus hated the diesel noise. Truck was like new when we got it.
Real good deal that you did not have to dig into your rig very far....That's always a plus...