Thorley BB/TH400 headers with a single output?

[hubcapboy]

I'm just about completely worn out from looking at header combinations all day. I really want a header setup that exits with a single 3" flange, so that I can run a single 3" muffler.

My setup is a '68 with a big block and a TH400. Thorley only makes a dual setup for that year, and won't promise me that anything else will fit. There are two options to get around this, and both involve plugging o2 sensor holes and grinding off heat riser tubes.

Setup 1: 1990 'Burb. This setup runs the crossover right under the pan. Here's the installation PDF with a picture of the assembled header on page 7:

http://store.summitracing.com/instru...%2D399y1%2Epdf

Setup 2: "Class A Motorhome" This setup is closer to running two short headers, but having a pre-fabbed Y that will bring it over to a single output. best pic on page 7 again:

http://store.summitracing.com/instru...%2D306y1%2Epdf

Please, anyone who has knowledge of how the chassis changed from '68 to '90, chime in and reassure me that the Suburban header will fit!

thanks,

/g