I have acquired a set of Aerostar springs for the front of my 55 Customline. Now, I need to replace the rear springs. They are worn out and basically flat. I read that Jamco sells some rear springs, but they are priced pretty high. I had pondered having a set made, but I need to know spring rates etc. I figure I could have a set made and save enough to buy good rear shocks etc. I would love to be able to lower it without having to use blocks. I have a set or 2 of different heights. Just don't want this bottoming out if I take friends along. Anything factory that will interchange, like the Aerostar front springs?