[gmc684x4]

What are your short term and long term goals?
Are you keeping it numbers matching ?
Being original motor i would change the pan gasket as well and check to see if the lifter bottems have mushroomed out

Vortec 350 can be found on the cheap on many late model ones i notice if it has a fuel pump block off plate its a 4 bolt main
If you scrounge a used vortec there prone to leaky intake gaskets express vans run them as late as 2002

Ls swaps can be done cheap if you research it and put the sweat equity into the swap