You can do the piston rings with the engine in the truck. Not ideal, but you can do it. I did it in my driveway over a Saturday and Sunday. You'll have to drop the pan, remove the manifolds, take off the head and then do each one. It's tricky to get the bearings all back on right while working on your back, but it can be done. It's a good time to take the head and have the valves and seals done by a machine shop.
I had low compression prior to doing mine, and was really glad I did it- I also learned a ton. The green bible has all you need.
1976 RHD Series 3 - SOLD
1989 Land Rover 90 LHD
1940 Piper J3F-50 Cub