[Mike C]

To Tim's point, the 3 speed shift linkage and the cross shaft for both 3 and 4 speed trucks, you need headers that are designed to clear that. Corvette headers look like they would work. Comparing a set I put O2 bungs in, they look exactly like the Heddman 4x4 headers I used to have on the Jimmy

In order to tuck the exhaust with the auto trans like your 72 has in your signature switch to the Lokar shift linkage, the longer one. 29" I think? Then you can run the Chevelle shorty headers.

I'm planning on running the Corvette manifolds on my 69 with the big block swap and running the exhaust up high. I have cut 4" tube into the crossmember to keep it high all the way out the back.