I don't know what your spring looks like. I assume you do not have any springs on either side to use as a comparison. Why do you not have any? There are many springs and spring kits that start with "H". I use them all the time. You will need to find the springs you need from a donor and use them outright or use them to compare what's in the kits. You can buy all kinds of kits at O'Reillys and find a match without opening the bag. Take back what ever does not match. There will be big trucks that use that same "Twin Action" brake. Some Big Bolter in here will know what to do, in due time. Keep checking your post. It's not good to abandon those helping. H7270 is a universal part number and is probably for regular duo-servo brakes 100 and 150. Don't worry about what the applicability says if it works. Most parts places don't go back that far and GM used many parts from the past forward. That's how I find all my hard to find parts. H597 looks very similar to your springs. They won't be color coded like the book says and you won't know the spring rate. What chassis is this? 1.5T ? 2T? School bus? Springs will probably be the same as a Chevy. 14 Bolt, more modern, diff may work depending on what you are doing with it. Driver-yes, hauling-no.
