[copper128]

I'd recommend against the Addco bar. The have an inferior mounting set-up and are too low and look lousy when installed.
Use a factory 71-76 rear bar. I'm pretty sure Dedsleds has one available. It's a simple installation and looks clean and "factory".

I installed one on my '67 Olds 88 and it made a very noticeable difference in handling. See my post on RealOldsPower.com for details: http://72.22.90.30/phpBB2/viewtopic.php?t=24880

I'll second the air-lift bag recommendation, much better than air shocks. Also make sure your brakes are in top condition before towing. Set up the trailer brake controller to apply the trailer brakes slightly before the tow car's brakes start to grab.

Glenn