I hear the knock you are concerned about. IMO it's normal IDI clatter. How many miles on the injectors? Recall the way you know the timing is correct is to bring the truck up to 45 MPH and keep it there a time. Then roll into the throttle: the IDI clatter should go away as the precups heat up with throttle added.
As you have an oil leak I would replace the seal and inspect the keyway(s) and key for slop. It may be leaking from the crankshaft bolt vs. the seal. Although I never did it: I have seen it recommended to use a sealer on the HB to crankshaft.
About $8600 to your door for a longblock per site sponsor link below. Not bad for a NEW engine. These GM cast engines are known as SCRAP in the PER world due to being crack prone. (Professional Engine Rebuilder.) IMO Spend the extra on a NEW engine. Further Twisted Steel Performance
@Twisted Steel Performance is also worth a call about these engines.
leroydiesel.com
Patch would still be running around IF I ever found enough cash to have had dropped a NEW engine in it.