Converting your 2wd truck to a 4x4 will not be a bolt up operation, some fabrication will be required to make the 4x4 suspension bolt up, mainly in the front. An easier route would be to swap the body from your truck, along with then engine and trans if you want to keep them, into the Suburban chassis. The 'Burb is only about 2 inches longer in wheelbase than your C20 (129" vs 1277" ). You will need to swap motor mounts to do this, and an adapter will be required for the transfer case. A little forewarning, that 'Burb looks to about a '78/'79, it should have the TH350/NP203 full time transfer case combo. I'm not 100% sure if a manual trans adapter is available for it, especially for the SM420 that your truck already has. The NP203 was only used with a manual transmission for 2 years, '74 and '75, and is very rare to find one that way. Advance Adapters would be the best place to check for that.
