72 C10 payload

[bullmecha]

Hey all,
Lurked around getting info here for awhile, great bit of reading I will admit. My issue is this, can I raise my payload capacity by getting different coils on my truck? I use it as a DD but i do actually haul loads most of the time. Maybe my originals may be worn out but I loaded it today with 1 4x8 3/4 ply, 12 2x6 8ft, and maybe 16 2x6 4ft. I was gonna keep adding but she squatted down to just below level and it is stock height. Any advice is welcome. Thanks and keep that info flowing.