Has anybody used these headers?

Centerdump shorties don't work in A-bodies. Forget about them.

In addition to 72blunblu's post, I would say a lowered stance and headers need to go along with upgraded springs and shocks.
I'm running 1" torsion bars with Doug's headers.
While I'm running the car a fair amount lower than stock, the headers are still the lowest part under the car and had to adjust it a tad higher again than I wanted. But with the my current ride-height the headers hardly ever hit anything, unless the speedbump is just a idiotic high, sow speed one in certain citystreets.