That pipe could be for wipers or other vacuum operated equipment? To determine what is and what's not original, it is best to find some vintage illustrations, such as from the owners' or repair manuals. Here are some of the things I see on the pictures: bed is likely not original or modified, rear view mirrors do not look period correct. Obvious - turn signals, side markers, etc. Interior appears to have been redone.
Under the hood: is that a DIY PCV setup? You might want to check the original fuel bowl next to the pump, it needs to be cleaner. The heater outlet has been welded shut I see the vacuum advance next to the ignition distributor but do not see a vacuum line going to it, is it still there? Also, is this engine original to the truck (does the number match the frame)? The red color seems a bit unusual. Also, either your brake or clutch pedal is out of alignment, they should be the same height.