I have changed the rear main seal on the engine stand, and while the engine is in the truck. When the engine is in the truck, I usually do not unbolt the rear main seal HOUSING from the engine block, as it will be more labor intensive to do that, since the oil pan also bolts to the rear main seal housing.......unless you also have removed the oil pan prior.
On the engine stand, before I install the oil pan, I install the new rear main seal into the rear main seal housing first........then install the housing onto the engine block.......this way you don't need much room at all to install the rear main seal. You just need enough room to work the inner lip of the seal over the end of the crankshaft, and then align the housing to the engine block and install the six 10mm headed housing bolts (about an 1" long) and torque them to spec with an IN/LB torque wrench with a shorty 10mm socket.
Here is a pic of the seal & housing installed while on the engine stand....I also use longer bolts in my engine stands, as I like to install the Flywheel while the engine is on the stand also.....
Here I installed a new rear main seal with the engine still in the truck when replacing the clutch also.....
I drilled a small hole (with grease on the drill bit to catch the metal filings) in the metal portion of the old seal, and screwed a small sheet metal screw into the drilled hole, then used a door panel tool to pry the old seal outward.....
Important!!
Keep in mind that when you re-install the flywheel, you need the flywheel bolts clean and free of oil, along with the threads in the crankshaft! You then need to put a thread sealer (I use RED LOCTITE... yes you can remove them later on!) on the flywheel-to-Crankshaft bolts. Those threaded holes in the crank go all the way through the crank, and they WILL allow oil to pass through them and onto your clutch disc if you don't seal them!!
