Signetroar, Back in the '70's I modded a set of Appliance headers for a '67 A-body to fit my '66 Valiant. It required two redirected pipes on the drivers side to go around the steering box & two pipes on the passenger side to clear the idler arm.
At that time I couldn't find under chassis headers. One problem I had was with the clutch linkage. Not from the headers but from the clutch.
Stepping on the clutch pedal caused the dashboard to flex. I made a brace from the master cylinder to the fender well. You also will need to reinforce the pivot located on the fender well. Mine cracked.
The z-bar needed help too. Gussets & braces.
My first pressure plate was a 9 1/8" Weber with 9 springs (OEM had 3 behind a 273). The 340 had a 10 1/2" Zoom.
The linkage failure didn't take very long.
Ed
