It's because with modern tires, you normally want way more caster, and many times run out of adjustment with the factory pieces, read on:
If you do some searching here about disc brake conversions, suspension beef, and alignment, you'll find that you don't want to align these to the old specs, with radio tires
Start by reading this:
http://www.allpar.com/history/mopar/front-end-alignment.html
Notice the "skosh" chart for alignment specs. These cars, "in their day," with bias tires, were aligned with LESS caster and completely OPPOSITE camber. That is, they (then) had the tops of the tires pointing OUT with positive camber. Now you want the OPPOSITE, you want the tops of the tires IN for NEGative camber, and you want much more caster especially with power steering.
If your old power box is in good shape you can re-use it. There are all kinds of routes to go with this.
You really need to do some reading and searching here. There has been TONS of stuff written on "what to do" with these front ends and "how to do it."
Stuff you might "fall into." Around 73, I think, the power box spline was changed to a larger size, AND the studs on the pitman arm and idler arm were reversed
WHAT THIS MEANS is there are FOUR parts that MUST go together depending on small spline vs large spline steering box.
The box must fit the pitman, and the pitman, the idler, and the center link must all match. The dividing year for the studs orientation was 67--72 and 73 / later
Here
http://www.forabodiesonly.com/mopar/showthread.php?t=236925
The other "trouble" is that in 73, Ma changed the front anti-sway bar, meaning, later one goes up through the hollow K member. Before that, underneath. This means the tabs on the lower arms are different.
If you buy an add on aftermarket bar, it's going to "depend" on what you get
I am certain, that you can much more easily improve the handling of "what you have" rather than hacking that front clip under the car. These parts are still available, and in the collector car world, "not that expensive."
