So before I go any further, if there are any amateurs on this forum like me, here's a quick tip I just learned:

Checking the pull on a timing chain is way easier grabbing the belt and fan-pulley from on top rather the bottom pulley. I did the bottom way a couple times throughout the process and found nothing. I just did the top way and found about 5/8" pull.

What I don't understand is, if my chain's stretched enough to make the truck run this crappy, howcome my timing looked like it was perfectly at 0? Would it not waver?

 

Well it can look like its timed but you need to get certain pistons to TDC (top dead center) to acurately check the timing and do valve adjustments and clearances if needed

and what year and engine truck do you have? i have a program that can give you the exact directions.



and if it looks perfectly timed but runs crappy theres a slight chance you experienced valve float which will knock your timing off

 

It's a 1992 Chev 1500 305tbi... hmmmm...