factory suspension for 1/2 ton 2WD suburban

[nm78bronco]

I am going to restore the suspension of my 1/2 ton 2WD suburban to factory specs, however, I'd like to put the maximum-capacity factory recommended springs for my truck.

The vehicle is a 1976 GMC C15 suburban with a 454 engine that I plan on towing with.

1976 GM brochures I have show that the rear spring rating for 1/2 ton 2WD suburbans was 2000lb each, while the front coil springs were rated at 1700lbs (454 engine) each. Does anyone know if GM ever used higher capacity springs for the front and/or rear suspension including all the other years of 1/2 ton 2WD suburbans made (1973-1991)?