If you get something that is unusual in the way of a vehicle why change it? My ambulance has repairs on it dating back to at least 1952 when she was rebuilt. I'd argue that the repairs changes are part of her life, they are her fingerprints of history! (Sounds pmpous dosen't it:D ) There are oddles of Jeeps out there, how many like this one?
All this lot of official balderdash to earn your living, and they worry about your blood pressure! Last medical the nurse got all frothy and told me I'd be on blood pressure pills for the rest of my life! Ten miutes later it was down to 80!
What I did see done on a Quad was to cut the top off the old tank, take out baffles and fit a new plastic fuel tank inside, then braze top back on. You do need a couple of vent holes hidden in case of vapour build up, but it worked.
Possible explanation is that when the Conventional Arms Reduction talks/treatys between Soviet and Nato retired AFV's were required to be destroyed under witness. A lot had cutting charge tied round them and were permenatley sliced. http://en.wikipedia.org/wiki/Treaty_on_Conventional_Armed_Forces_in_Europe