I'm the "Bolter" that PM'd Phak1 about his post trying to identify his rear spring set-up. I also have the same rear spring set-up on my 54 Chev 3100 Hydra-Matic and always wondered if these were an OEM Chev part or an aftermarket part. I may have found them on page 434 of the 1929-1954 Chevrolet Master Parts and Accessories Catalog. Listed below in the 7.503, Spring Assembly, Rear section. 47-54 Util 6 leaves (Aux Springs) Part 604934. I'm attaching photos of my set-up. Hope this helps.
