I had a local manufacturer make a couple pair of 1/2" one pc mono-leafs for me to my specs.
John Calvert advised me what to look for as far as measurements relating to ride hgt car wght and spring arch. This was 10 years ago.
Back then we were discussing the feasability of fiberglass leafs, dont know if it ever came to fruition.
If I recall the six banger springs are identical left and right, you have to look at what you have.