Some data from a post on Pirate, but the data was questioned on the post:
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Heres the low down
4 leaves in the front only, 39.75" long, and a rate of 128 pounds/inch stock and 203 pounds/inch optional (6 cyl and/or hard top).
Rear has 5 leaves stock and 6 leaves optional, 46" long, and a rate of 170 pounds/inch stock and 237 pounds optional (6 cyl and/or hard top).
4 leaves in the front only, 45" long, and a rate of 113 pounds/inch stock and nothing optional.
Rear has 5 leaves only, 45.6" long, with a rate of 170 pounds/inch, nothing optional (no heavy duty).
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So, I would say what you have is an optional 6-leaf rear HD YJ spring, going into a 4 cyl YJ front. Probably be really stiff. Personally, I would take a leaf or 2 out, until what you're putting in and what you're taking out feel about the same when you jump on them. [img]/ubbthreads/images/graemlins/smile.gif[/img]
FWIW, here are my 5-leaf YJ rear springs that I put in my YJ when I went SOA. I put a 6th leaf in the rears, which was another main leaf with the eyes cut off. Notice they have 3 clamps, and rounded ends. I have also seen tapered ends on some springs. I seem to remember an article somewhere (maybe in JP?) that talked about the different types of YJ springs - round ends, tapered ends, etc.)