Without the wrecker package, I imaging it would he a little less than a standard 800 series cargo truck. Probably between 18,000-20,000 lbs.
Not sure how much the bed weighs, and the 800 series comes in at a hefty 21,020 empty.
Looking at the dash, it has the warning about putting the transmission in 4th or 5th speed before using the crane and winches.. so it very well may have been a wrecker... I don't know enough about the wreckers to say... maybe @m715mike would know... I hear he has an 800 series wrecker...
First suggestion (as someone who has recovered MVs from the current state of yours):
Long pants and a weedeater!
Here was my M37 when I first saw her...
On a serious note, clear all of the growth as much as you can before trying to move her... you have no idea what's under and inside...
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