There were at least 2 metal 75 USgal DT designs used on the P-47/P-51 - one was steel and the other was aluminum.
Check and see if it is magnetic.
If the one you found is steel it would have weighed 50 lbs with its associated bits and pieces (ie fuel filler cap, overflow hose, the attached hanger points, etc).
If it is not magnetic then it may be the aluminum type. Unfortunately I do not have the weight for that one, but it should weight significantly less - probably around 35-40 lbs.
There were also at least one resin-impregnated plywood type and one fibre-impregnated rubber type.