1966 C10 Hauler?

[AzCountryman]

I have a 1966 C10 1/2 ton with a 327 and the 3 speed TH350. Does anyone know what its rated for towing? Cant seem to find anything online.

Also whats the best ways to ups its rating......Guessing I could put 3/4 ton springs or 1 ton to help hold the load? beef up the tranny? Different gears?
Not sure what I will be wanting to haul but guess I never know what life will throw in my path and would like to be prepared.

Has anyone beefed up there C10 for hauling?

Also there is a plate on the drivers side just inside the truck...its pretty worn but has some #'s stamped on it. 5000......Z62......540.....127.
What do those #'s mean?
sorry cant post a picture right now work computer wont let me go to photobucket.