I'd say there's no need to replace the main leaf to beef up the rear or front, just add leaves.

I purchased the sorriest garbage you could ever call springs from Eaton Detroit Spring Co., complete new front with either 500 or 750 lbs [can't remember which] overload rating from stock. They sagged flat in 3 months and had the spring shackles against the frame in 6 months.

Eaton wanted me to pay return shipping to inspect them, plus a second return shipping IF, that is IF they decided there was a problem. Either way I would have had to pay the freight for original shipping, plus return freight for inspection, plus return freight to get them back or receive something that actually worked. Shipping was as much as the new set of springs! Their complete new springs with 500-750 lbs overload were worse than the stock original 45 year old front springs.

Went to a buddy and pulled a set of rears off a 60's Ford truck, used about 6 of those leaves along with the main leaf junk from Eaton. Worked fine, springs are same width as Dodge. Just adding leaves will solve the problem. Try to build a spring pack with progressive increases in spring leaf length in the pack like factory did with OEM's. This prevents stress which could break leaves.

Some Dodge had progressive weight rear springs, where there's a main spring pack of 3 or 4 leaves, then a 1" spacer block, then a second spring pack closer to axle of 3 or 4 more leaves. With normal driving a smooth comfortable 1/2 ton ride, but when you throw a load in it settles to the second set of overloads for a much higher 1 ton spring rate. I have this setup on my D300 1 ton and they work very well. You can do the same or just build up the entire pack as one.

By the way, I've installed Air Lift airbags in the front of mine, which required a custom build of upper mounts, and they're great! Adjustable for any kind of ride I want.
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