I run dual flowmasters and dump them before the axle. I have a MP# of it if you would like to hear it. Email me and I will send it to you. Also here is a link to where I have pics of my exhaust set up.
http://www.geocities.com/cjhicks1/exhaust.html
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BRANDON
1979 CHEVROLET BONANZA BIG10
350 GM Crate Engine ZZ4,1406 Edelbrock, 1 5/8" Heddman Headers
2 1/2" Dual Exhaust with X pipe and Flowmaster 40 Series Mufflers,350 Turbo Transmission,3.07 Gears
My website for the truck.