That there is electric -- the wires on the side would be the giveaway -- and is an 8000 # capacity.
I have one just like it, only one that hasn't been submersed.
They are indeed rebuildable; all parts are available from Ramsey. If you CALL Ramsey, however, they will refer you to a local dealer, which can be a clusterfsck. Instead, get the NEW part numbers for what you need from Ramsey while you're on the phone (for the original numbers, see below), then order the parts from
http://www.ramseystore.com
Now, I have an exploded parts diagram with (old) part numbers for this thing ... knew I've been keeping that around for a reason!
http://brochures.slosh.com/index.shtml?blazer
and click on "Ramsey Hidden Winch" on the left.
Note that this mounting style is different from the modern ones, Warns, etc ... this style is often used on tow trucks' flat beds, for instance. It also conveniently fits between the frame rails of our trucks, albeit a bit low, but there was a kit to do this on the 73-80's, the instructions for which are on that same page. I also have CAD drawings of the parts involved -- they're basically flat strap and angle iron, nothing special -- if you want to do this.
Finally, the motor is a pretty standard item; you can get replacements on Ebay for about $130-140, a new one from Ramsey for like $200, or I had a local starter shop redo mine, $85 IIRC.
HTH, and feel free to PM me with Q's. I've just been through mine recently.
-- A