This sounds crude and like something you might be scared to try but it worked for me...Get a ratchet strap and wrap around the collectors on both headers, so when you tighten it up, it draws the headers closer together and off of the torsion bars. If you don't have a crossover in your headpipes, weld a strap across the headpipes to hold the headers in that position. If you do have an H pipe, shorten and re-weld it. Remove the ratchet strap and drive it. Eventually, they'll stay that way after heating a cooling several times. Worked great on my dad's road runner. Only other option is to nearly remove the engine to get the headers out and beat the crap out of em w/ a hammer for clearance.
Did this almost 10 years ago to his car ('69 road runner, 440-6 w/ 906 heads) and never so much as hurt a header gasket...one thing I kinda figured might happen.