Too Rusty

[smart68]

I have a 79 c20 my dad purchased in the early 80s and used for hauling water to the farm. I have been planning on using the cab to build myself a short box step side. I have the frame for the step side and the box, both need work but its doable. I planned to use the front clip, engine, tranny, and whatever else is useable on the 79. The problem I have run into happened when a friend and I started to replace the floor and rocker panels. The rust has worked its way down to where the crossmember attaches to the cab. It is very bad and my friend says it isn't worth fixing. I have looked for other peoples projects on the internet and have found some but they are all further along than I am. I have already scrapped my 68 because of rust and bondo and now may be on the verge of doing the same to this one. Is this problem fixable or do I gather all my pieces and parts and start listing them for sale? Suggestions?