[gmc684x4]

I am going to say your tranny is Sm420 if its a 4 speed possibly a Sm465 if changed from a 69 and up truck unless its a 3 speed

Undo the bell house to the motor there a 9/16 head 3/8 bolt pull the bell housing with the tranny

Remove the shifter boot on a 4 speed from the floor slide it up push down on the ball cup on the shifter turn counter clockwise release and remove shifter by pulling up best doing this with it in neutral

I have always leave the engine in the vehicle when doing a clutch job why make more work and replace all that antifreeze if you do not need to
and having an extra jack to support your engine with a block of wood on the cup to help from denting the oil pan
I did that last with my sentra everyone says pull the engine. too much extra work for little gain

and to the comment pull the engine do you have an engine hoist to do that extra work ?