Why are there 2 different mufflers for an 85' Chevy 6.2 one costs $66.00 the other $90.00 to $125.00? Does back pressure have something to do with it? I've had these trucks since they were new, and have plowed snow with them for 17 years. I just don't remember there being a difference in the cost of these. ??? :'( 99' 2500 Quad swb ctd 24v for a real truck!

 

Concidering the age of the truck I personally would opt for the cheapest one. I had a boss that had a 6.2 (long time ago) and he put glass pacs on his truck. When you go on it the sound was great! The only worry I had was it was so loud that I was concerned about the cops with the noise.
Tom

 

This is the price difference between the left side, and right side.

 

I'm going to guess you have a 3/4 ton. The left side fits all 6.2s from 82 to 90. The right only fits 82 to 87 c10-c20 standard wheel base. Can you say "supply and demand"