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 and year.
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.
It will save on shipping
http://www.atlassuspension.com
https://deaverspring.com
https://northcountyspring.com/
Eaton
https://www.eatondetroitspring.com/d...L%20-%20283cid
SRI