If you have stock exhaust manifolds handy for the 4.8, 5.3, or 6.0, please measure the port diameter and distance between studs on the outlet side. Also do tell what engine they came off of in case there is a difference.

I'm planning a catless y-pipe and would like to know if there are any differences between the different factory manifolds.

Thanks!

 

Don't know about the 4.8, and can only speak first hand on the 5.3 & 6.0 differences in the 2003 trucks.
I was going to put an SS Silverado exhaust on my 03 ECSB of yore. I was looking for a direct swap out but the cast iron plumbing stopped me. I did not want it bad enough to pull the cast iron off.
The 6.0 has the same manifold to pipe connection on both sides. The 5.3 does not. If my memory serves me well the 5.3 manifold is the one on the left. The bolt pattern is not even like the 6.0's is, and there is a floating flange that is pulled up onto the rounded boss. I believe the 6.0's a copper o-ring. The 5.3's drivers side connection is the same as the 6.0's.

 

that's extremely helpful... and also complicates my plans somewhat.

Thanks!

anyone else?