As for what they are worth, not much, basically scrap price if even that and I'd say if you were trying to sell it rather than buy it, you'd have a very hard time to even find anyone wanting it, let alone pay much of anything for it, if that says anything for its value on the buyers end.
Check it all over, the largest thing I've found is does it shift through the gears and give it a run around, as for oil leaks, the largest thing I've found with mine is the steering cylinders and if they leak, they have a gland that you tighten up and it squeeze's the seals together, those glands have a lip inside that tends to break off, those parts are no longer made and most in the junk yards are also broken, I had to have a shop machine new one's for mine, without them you have a large boat anchor, hoses are no big deal, and mostly reusable ends on them to fixing is cheap and easy.
The Allison auto has a gear box on the back side of it, inside there are gears and bearings that are obsolete, if I were to buy it, I'd pull the cover off and see what style of bearing is in it, along with the flat gears, depending on the model year and if any updates were done, the newer version can be replaced, the older version is beyond hope. If you buy it, replace the bearings to save the gears set no matter what version of gears are in it. I've been told the newer version is the same as a 14b and those are still available. I spent about a grand on gears and bearings to do mine a year ago, used gears new bearings.
Check the cutting edge for wear and see if the edge has been flipped already or if you need a new set of cutters on it, check to see if the blade holder has been welded up or worn thin, you'll need a new cable for the pan gate lift, no big deal, but needs to be done. As for the top back portion, as has already been said, someone knocked it off while top loading it, not a big deal either.
If you buy it, make sure to change the hydraulic filter, those are only paper and once the paper comes apart, the paper debris ends up in the valve and causes serious grief, same for the suction filter in the tank. Change the Allison filter as well, its a paper cartage style in the side of the Allison auto.
Make sure the steering pins take grease before you buy it, check for play in the those joints as well, those are a bugger to get out, you'll flame them out with a blow torch to replace them, if the joint is worn too much, I'm not sure the scraper is worth fixing or buying. Best of luck.
