"Gas shocks" raise the ride height very little. Same with the "coil over" rear "Load Leveler" shocks. Shackles do NOT work on Chrysler rear springs, the main leaf gets bent down rather than raise the car.
You CAN put more pre-load on the front torsion bars, though, but that also increases the spring rate for a much more 1-ton truck type of ride.
How much air you put into an air chock to raise the rear end can and might cause some damage. For example on my '70 Monaco 4dr hardtop, I used them to level the car to normal ride height, in the rear. 60psi is all it takes to raise it one inch, with the front end set at specs for non-HD suspension. Compared to the minimum to inflate the air bellows of 30psi.
I started doing that in 1976. No issues. BUT I am in Texas and not New York or Canada. Difference is the use of salt/de-icer used on the roads in the winter. Salt spray which can get onto the noted upper shock support and cause underbody rust and related "flimsiness" and failure. My car was sold new down here, not imported from other parts of the nation.
I'm suspecting the northers associates who used air shocks to raise their A- and B-body cars to clear N50x15 tires (in the late 1960s and such) on the rear used much higher pressures and lost most of the compressibility of the rear springs in doing so. Which put ALL of the ups and downs directly to that upper mount. I never did hear of any failures of that upper mount bar down here, but there obviously were up north. I kept seeing those cars for several years, back then, until the owners got married and needed a bigger car to haul the new family in (not a hot rod, usually)
FIRST, you need to get a copy of a Factory Service Manual for a C-body car in the 1974-1978 model range (which can be similar to your 1977 car). Make sure teh front suspension is at the spec'd ride height adjustment. With the car on an alignment rack, compare the rocker panel heights (from the "road surface" to the bottom of the rocker panel). The design-height is for the rocker panel to be completely parallel to the road surface, period. Which is reflected in the photography art in the sales literature.
Once you have done that, you can determine how low the rear of the car is and how to best approach getting the car level again.
www.detroiteatonspring.com for prices, specs, and such for the rear springs. Other spring suppliers exist, but Eaton is supposed to be building them to the OEM specs they built the OEM springs to when the cars were new. Getting new ones means that your old springs are not being "refurbished" or "reformed "with heat and cold processes to "industry standards".
Just some thoughts, my experiences, and observations.
CBODY67
