Cab floor structure question

[Drive-In 4x4]

Hey guys I found a Super Cheyenne that I'm interested in....I know cab corners are a common problem and rocker panels but what about the floor reinforcement structure? Not sure if that's what they are called but the truck I looked at had some structure close to the rear cab corners that was ate up and in front on the same kind of floor support structure. Anyway is this a big deal or can I buy new ones? Drill out spot welds and repace??? The door bottoms are also ate up on both sides and the front fender bottoms are toast as well. The rain gutter above the driver side door is a little rust also. What do you think is the deal? According to him he said the guy he knew had it for years in the garage and then he got a divorce and then it spent sometime outside for a few years. Anyway the truck has been repainted at some time because the clear coat is coming off. Anyway the truck has the normal problems plus a few extra but it's all there and runs. It still looks pretty good but I'm just wondering if the items I described above can be fixed? I have another body in my garage that may yield some donor items.....Thanks and what is the name of the best place to pick up some new sheet metal for this as well?