The IT-60 was designed SPECIFICALLY to be flat towed this way. The mast uses bar-hanging forks, and has flip up clasps to rotate the forks and secure them to the mast. It has headlamp/taillamp assemblies on BOTH ends, with a connector at the chassis, and connection points for a tow-bar with integrated master cylinder that coupled to the lift's drive-wheel brakes. The steer axle (under the counterweight, as usual) is on svelte leaf springs AND a center pivot (mine has shock absorbers, but I think they were an add-on) and the steering knuckles have negative camber and caster so that it will self-steer around corners.
The steering valve is an open-center/non-feedback unit, that when there's no pressure from the main pump, will allow the wheels to steer themselves. The IT-60's pump, however, is a vane-type pump, so when flat-towed, that steering valve will NOT get fussy and argue with steering motion.
The IT-60's drivetrain is interesting, too... mine is a 225 Chrysler Industrial slant six, connected to a torque converter, going into a Clark-made F-N-R planetary box, which then is linked to a 4-speed Clark truck transmission, to a very stout Clark full-floating axle... with hydraulic brake cylinders on drum shoes, with a pair of very unique drive wheels and a pretty odd-size tire that has an exceptional load and speed rating. With it's four speeds, bidirectional, with neutral. The torque converter has a 'dump' circuit connected to both a round footpedal, and also to one of the two brake pedals, so you can dump and inch by just the converter, or you can foot-brake to inch, or you can foot-brake by stall. Once you get it on a large straight path, you can put it in 2nd gear and really hustle down the street. Put it in 3rd, and you can get yourself a ticket. Put it in 4th, and get a ticket at just a little off idle... but I wouldn't do that...
But the whole combination of wierdness was all by design and intention, and IIRC my owner's manual identified 55mph as the expected (but don't exceed) flat-tow velocity. The machine is about 18,000lbs, so best be in a straight truck of 26k or over GVW, and it would be wise to be pretty close to rated before hitching on this thing. I don't think I'd want it behind anything less than 32k GVWR...and at LEAST weighing 28k.
As clever as it may all seem, it isn't what I would call 'good' in terms of actual use.
My IT's mast is a 5-section collapsing cylinder, with one segment going down, the other four go up. Hydraulically clever, but loaded with seals, and heavy as heck, so it's lifting weight AND the mast CG sacrifices operational performance and rebuilding requires a second forklift or a crane to lift the cylinder OUT for service. It's a cubic money expendature. I would have preferred a simple 2-section mast good to oh... 15ft or so, rather than 35ish...
The whole steering-valve/prime mover vane pump thing is an operator's bane. IF the engine is idled down to creep gently, the vanes retract. If you're trying to raise the forks, or tilt, and steer, while at idle, you'll have either one, the other, or (most often) neither, so you end up running the load into whatever you're trying to avoid. Good part is that the vanes retracted make for VERY EASY starting of the slantie (which starts really well on frigid days), but unfortunately, the vanes stay retracted as the engine warms, so hydraulic fluid doesn't circulate, and thus, refuses to warm up... (I'm changing several things to resolve this, as cold weather ops is absolutely necessary here).
As OP mentioned, the drive tires are special. So are the steers. Off road... well... yeah, but mine has issues that make the 'off-roadability' questionable. Since tires are wide, it WILL roll over surfaces that MIGHT not be as solid as what the high-load pneumatics on my Hyster H50H demand, but with the stupid-tall mast's CG being about a foot about the ROPS, well... it isn't going to successfully navigate anything that's less flat than... oh... probably an air-force runway in South Dakota.
Mine doesn't STOP worth a crap... and it has some funky habit of hanging up just one drive tire as you're rolling along, and nobody (neither the previous owner, CLARK dealership mechanics, or I) know why.
I have gathered parts for, but haven't done yet... a 'usefulness conversion' for mine. I've got a 20k Dana 2-speed highway tractor axle, dually... with about 7:5:1 and 10:1 ratio, big simple drums with air actuators. I've got a hydrostatic motor in a transaxle casing that has geared 4 speeds and a differential, as well as the matching variable-ratio pump (all from an IH 750 combine), and for the front (steer) a Rockwell 2.5T truck steer axle. The pump is already fitted with an adapter to bolt to a Chevy engine (because I had it) that will fit inside the compartment nicely using the Chevy clutch, and a hydraulic slave cylinder to disengage the clutch. I have a proper high-speed vane pump for steering, an engine mounted low-volume hydraulic pump for accessory use and warmup circulation, and the large--volume pump coupled to the back of the big hydrostatic variable for running lift and tilt. I SHOULD be able to start it cold (with hydrostat disengaged, and steering vanes retracted, so just the small hydraulic pump as parasitic load) and allow fluid to circulate, pass engine coolant through a loop in the hydraulic tank (to get it up to operating temp in winter), and once it's warm enough to operate, release the clutch to spin the hydrostat and run the forks.
Dunno what I'm gonna do about tires, but it WON'T be highway speed, and I since the 4spd hydrostat will be good for mebbie 15mph tops, I won't have to worry about overrunning tires' speed limitations. I may just run dual or triple 19.5's with snow chains or something... but with the other end driven, mebbie I won't even need chains, eh?