There's a trick on the I-beams, provided they're still forged - my '65 had such I-Beams.
I'll assume you also intend to lower the front end.
First thing you must do is replace EVERY SINGLE BUSHING AND MOVING PART. Leave nothing behind. Get it dialed as close to factory specs as possible, and then take accurate measurements and notes as to what your camber and ride height are.
You can then lower them in the same manner that you can a front axle on an '30's - '40's Ford by heating them up in a forge and stretching them with a hydraulic press. While they're still hot, you can also adjust the camber.
I cut the springs on mine for a three inch drop, which initially gave me a touch too much negative camber. By heating and stretching the I-beams, I picked up another inch of lowering, and was able to reinstate the camber angle. Additionally, with less suspension travel, the camber stayed closer to the at-rest camber angle while driving (less arc + shorter spring with increased stiffness = less variance in angle).
It's not a cheap fix, but it sure worked well, and contributed to a great stance and really decent tire life.
The trick is finding a Blacksmith who can do this kind of work. I had a buddy who was into sword making, and he knocked it all out in two days.