Extended shackles work on GM and Ford cars where the axle is more in the center of the leaf springs. They do NOT work on Chrysler products where the axle is mounted toward the front of the spring, forward of center. Period.
There are OTHER things that Chrysler did that Ford and GM did not do, too. As common and similar as the cars were back then, they were NOT "all the same". That "not the same" drove some people away from Chrysler products back then, just at it made some of us stronger proponents of Chrysler Products at the same time. WE knew, understood, and celebrated those differences.
No matter the brand of vehicle, whenever the REAR of the rocker panel gets higher than the front, it makes getting the specified amount of CASTER in the front end alignment more difficult as getting that adjustment completed depends upon how level the car is, sitting still. Less caster, less straight-line stability of the vehicle, especially at higher road speeds. Whether you use extended shackles, air shocks, front torsion bar adjustments, or over-arced rear leaf springs to do it.
Back in the late 1960s, a friend had a '65 Dodge Dart convertible. He put the longest rear shackles he could find (like 6") on it to raise the rear end on it. It MIGHT have raised the rear axle 1/4"! It made the rear section of the rear leaf springs "flat". ALL of whicih was on full display as the rear body section angled up toward the back bumper. Showing his intent and why it failed. With de-arced rear leaf springs.
I KNOW many in here will gnash their teeth, but the best way to get to what you wanted is "air shocks" (of which Monroe still sells them for many products). When I bought my '70 Monaco Brougham in 1975, it had seen trailer towing use. Already having "load leveler" "coil over" shocks on the back (and it still sat low in the back). With the closest spring shop 40 miles away and far too expensive to get new ones from Chrysler (if at all, at that time), I did the next-best thing and got some Gabriel Hi-Jackers rear air shocks tor it. Took 60psi to get the rocker panel level again (and the factory dual rear exh pipes not dragging any more)l. With those shocks, I can set the "rake" anywhere ai want it, but 60psi leveled it and that was all I wanted. Down here in TX, the rear shock crossmember is still intact, as I still have the car. For those who live up in snow country where salt is used and not washed off of the car's underbody, might not be viable up there, by comparison.
ONE other issue with a raised rear ride height is that the main part of the headlight beams will hit the ground far too close to the front of the car, highly compromising night-time vision "down the road" for safe freeway night driving. The headlight vertical aim is easily adjusted, though. Just don't adjust it so high it gets into the mirrors or sports cars in front of you.
CBODY67
