How worried do I need to be about this possible corrosion under the wax oyl?
How difficult is it to replace the rear panels with windows?
-Sam
covering rust in wax oil is literally how guys in UK get these trucks to pass inspection. You just have to physically check it some are not bad some are horrible. This truck is in about a million times better condition than mine originally was when I purchased it. One more note it's not a possibility of rust corrosion under this wax oil there IS rust and corrosion under the wax oil. You can physically see it and it's why it is bumpy and is why you have rust repair welds all over the frame.
You don't replace the panels you cut big holes in them and you put the windows in there. If you have to ask You aren't capable of doing it. You're looking at a couple hundred per side for the windows if you get them used, plus maybe $500 to $1,000 in labor for a local shop who's willing to do the work. Finding somebody willing to do the work is going to be probably harder
I don't think this truck is a lost cause but it's not a deal at 20k.
If you could get this truck for $17,000 and put 20% of your purchase price aside for repairs and deferred maintenance in the first year you would be off to a good start.
But like others have said expect to repaint it then expect to have corrosion issues essentially forever. Like every other truck in this price range.
If you're willing to spend around $30,000 or maybe $35,000 US you can get a truck that's essentially rust-free but original and not with pretty paint. You could then spend anywhere from 2 to $10,000 to prep the original paint for a good paint job to make it look like this one, and it will last.