I looked at some of the other pics that I took and noticed the 5,000lb limit stenciled on it. Not sure if they caught a problem or if it is just a precaution.
I know almost nothing about this type of truck. Could a guy use the winch for pulling trees and such or is this counter to it's design?
Not knowing these wreckers specifically, just looking at the truck and aproximating a couple of things, 5000 pounds looks like a pretty reasonable "pick" for that truck. That is, the dead weight lifted if you were going to tag another vehicle behind with the front wheels raised.
Those old booms are thin, and if used improperly you could probably collapse them trying to recover a stuck lawn mower, but if you watch your angles and what not, they are very, very stout. Pulling trees with that truck would require spades. But probably quite doable within reason. I think sequoias are out of the question.