Heavy Duty-ize my Light Duty 3/4 4x4... What Parts?

[Chris in Idaho]

I have a 91 GMC Sierra 2500 4x4, it's the 6 lug 3/4 ton. I use it as my daily driver and also to gather firewood. I made some bed side extensions that let me load wood up level with the top of the cab, and it really squats down under that load.
I'd like to swap in some heavier duty components (1 ton?) and I'm not sure what are the best parts to look for.

I'd like to swap in a heavier rear end and springs, which ones would be best? When I'm looking at donors in the salvage yards, do I need to find a truck the same body style as mine or will the spring perches and stuff fit from a 73-87 truck? What about gear ratios? Will 1 ton springs give me any lift over my original ones?

How about the front end? I know the earlier trucks had solid axles (I'd like one of those, but that's later), but what can I swap out to beef up my IFS? Which IFS components are actually different between the different weight ratings?

Lastly, what is the biggest tire I can run with the stock ride height? Will 33's fit?

Thanks
Chris