I'm gonna second that emotion with a guess at either a Hopto, or even a Warner-Swazey hoe setup. And yes, those old 534's were not a jewel on fuel.
I worked for a guy 25 yrs. ago who had a 1968 F-950 Super Duty triaxle dumptruck with a big giant 16 c.y. body. Had a 5 X 4 two stick trans., locking diffs. that were only rated at 38K if I remember right.
Also had a 1971 Brockway 361 with a 318 screaming Yamaha I used to drive. The 534 gas job would walk away from that Yamaha with ease while loaded every single time, but when the Brockway finally caught back up to the Ford, he was sitting at the gas station with the body elevated a couple feet, filling the thing back up. Used to stop 2-3 times a day for gas with that beast, but man did it have some bottom end torque. Gas was around .75 cents a gallon, around 1980. Unbelievable...
I got the privelige of running an old Sampson truck mounted excavator for some cobbed up old contractor years ago. He had this stupid thing for 25 yrs. and claimed it to be the best thing since sliced bread. Sliced bread wasn't even as old as this old junk. It was on a 1953 GMC 5500 6 wheeler chassis, with not even a sign of a brake on the truck. I got to digging a ditch on a slope with that thing, sitting out in mid-air on an old tractor seat, offset to the passenger side, pulling on about 10 levers to make it do it's thing. All of a sudden, she took off backwards headed down an embankment I know darned well nobody here would have liked to have gone down over, including me. Here I am, out in mid air, rolling like an s.o.b. downhill towards a sheer cliff, when I shoved the hoe in the ground with all the will I had, and it sent me doing a swan dive over the valve body and all those hydraulic lines, face first into the dirt. But it stopped, didn't run me over, and I just did a Rambo roll away from it when I hit the dirt anyway to make sure that old junk didn't crush me. I walked up to my crazy boss and told him to take his job, that old piece of junk and every other piece of junk he owned, and place it in a very common area we all know. Never even went back for my last check. It was on a Monday, only a few hours into the day, so he didn't owe me much anyway.
Never cared much for those "open air, convertible excavators" since that day. Luckily I lived to tell the story.