A 3,000lb. Spicer axle is the weight capacity of the axle, has nothing to do with the springs that were spec'd for any one vehicle build. The spring callout on the lineset will denote that line item.
Edit: the lineset you posted (and the one you sent me) is definitely not for the subject vehicle. The lineset you have is for a 4x4 regular cab pickup with a single speed transfer case. I also have the copy of the original dealership sales proposal out of abilene for the customer based in coleman and it denotes a code 02012 fa-12 (3800lb.) front axle "with comparable leaf spring" and a travelette body, the lineset you have now is not for a travelette. This is a sales proposal or what we in the business called a "front sheet" to take to the bank or lending institution, it carries no serial number data and does not specifically identify any one vehicle nor it's exact assembled package. Unfortunately the parts list and service manual don't call out the spring codes per se, though the actual part number for the spring pack is referred to but not by spring "rate".
I remember now about you sending me the lineset jarrett, I think it's filed in a folder I keep where we discussed all your stuff, same thing I do for anyone I work with.
The rear cab glass in the junker is good, no bubbles, no fog. However, that glass is available new from a navistar dealer last I looked since it's used in very late model medium duty trucks still. The rubber seal is still available new and as a reproduction part.
I'll try and get the measurement off the spring I have that is loose, I'll have to dig it out of the pile of shit that was stored in the bed.