Well, I bit the bullet and am finally going to cure my 4.9l's main bearing knock. The car is in too good of shape, and it bothers me too much to continue letting it knock away. After consulting others who have had experience with these engines, I have decided to replace all 5 bearings instead of just #1
Here are the current part numbers for the bearings if anyone is interested...
#1 position, service oversize: 3545719
#2 AND #4 positions: 12489577
#3 position: 3545721
#5 position: 3545722
There is also a service bearing for the #5 position as well, the number is 3545723 if anyone is interested. Good luck finding any of these if you are interested as they have all been discontinued. I live in Milwaukee and managed to find a set in Washington.
Anyway, I am going to get at it tomorrow, I will let you all know how it goes.
For others information, maybe GM discontinued the bearings but Rockauto.com has full sets in stock, brand name too. (Clevite and Sealed Power). I seldom go to a dealer for parts unless it's the only choice. I needed a fuel injector clip for my 4.9, dealer said a 2 day wait for an 8 pack. NAPA had them in stock, sold singly.
My point is, don't restrict yourselves to the dealer for older parts. Just be aware that hard parts for 4.xx engines are getting expensive.
on the contrary what you want for your number 1 postion is the "blue" bearing for the 4.9 liter, it is a .032mm undersize bearing, if you put any other bearing in the number one position it will knock again.