Rear suspension swap
Go find a mid 80's vintage gm car with 4 link coil over rear suspension. get the whole car as a donor for your build. The key measurement here is the distance between the rear brake drums, should be plus or minus 1' to have a good fit. The frame width can be adjusted to application. The gm box frame can be slit to open up the channel to fit existing frame rails of the 52. Minimum overlap at frame splice should be 6". More is better! Set it all up and then weld it inside first on overlaps and then beat the late model lap on the inside into the frame of the original frame and then weld that up. Be sure to grind all welds and check for any imperfections. Reweld again for a better looking finish weld. If done right it is difficult to detect where the frame was altered. Use the late model driveshaft to get rid of tourque tube. Do not adjust or tweak the original frame rails. Be creative with the donor frame to get the proper center and width alignment. If you are really a screw up, then you can always start over with another late model frame.... The original 52 frame might be hard to find.... So don't monkey with that!
Once you have the 4 link fit and installed, cut it off to the rear anywhere past the coil pockets and then add the original frame back to the rear section. This allows the original frame section to be used so that gas tank hangers etc. can be used. Also bumper mounts will be correct and rear body mounts will fall back into correct position.
I have done several set-ups this way and end up with a really nice finished project.... Measure thrice, check it twice, tack weld, remeasure it two more times, scratch your head..... ask your buddy to check it. Then disreguard his rantings... Weld it and be done with it. It will be fine! If a uaw worker can put one together so can you. Do not forget to find a olds , or pontiac rear anti-sway bar assembly. This simple addition really tops off the job and the car then handles great.