Any leaf spring manufacture should be able to build your spring. This is from the SRI Leaf Spring data manual V17. All they need are the first three numbers Stock no. 48-881, M.L. No 48-879 and your part number 2444869.
Eaton has this spring listed under CHEVY C20 67 68 .it’s the same as the GMC but the Chevy part number is 3920437
You live in Los Angeles ca. Here are some spring manufactures near you.
Its will save on shipping.
http://www.atlassuspension.com/index.html
https://deaverspring.com/
https://northcountyspring.com/home
Eaton
https://www.eatondetroitspring.com/d...L%20-%20250cid
SRI