Best coil springs and shocks for '72 Fleetside.

[sof]

I bought a 1972 1/2 ton fleetside (coil springs front and rear) and I want to keep it stock stance but improve the weight carrying ability somewhat. The factory shocks and springs need replacing and it had, as an option, HD rear springs from the factory. I would like the best variable load springs all around and the best front shocks and was thinking of air shocks in the back to improve its ability to carry more. Should I go to 3/4 ton springs and shocks? Any and all suggestions and thoughts would be appreciated, thank you in advance.
Guy