Yeah, those early 580's were built on a 535 tractor - not only could you get it as a 3-point or hoe, it was also available as a beefy fork lift where the seat and controls were (IIRC) turned around. Didn't pay a lot of attention at the time, but the 6" thick manual I bought for it shows the fork lift in its own section.
Downside - you can't have a PTO unless you're willing to remove the rear plate on the transaxle and swap it out each time you add or remove the hoe, because by my measurements the PTO would interfere with the hoe. This would also mean draining/refilling the transaxle each time.
I considered trying to make a hydraulic motor PTO setup that would hang on lengthened studs at the rear of the transaxle, then came to my senses and bought an actual "farm" tractor (no FEL) just for those "other" uses.
Oh, sorry - yes, I have a set of forks I built - 2x6 tubing, ends sectioned and re-welded, they just slip over the cutting edge and there's a section of 1/2" x 4x4 angle welded in the rear at an angle, that rides up right behind the heel of the bucket and has a 1" hole in it which I cinch up to the top of the bucket in back - they're very sturdy (picked up about 2500 lbs with 'em so far) but the blind bucket is a deal breaker without a spotter.
I now have a 6' Caroni flail mower and a 6' Priefert tiller for the AC 160 tractor, and am scheming on building a "power hiller" by adding a pseudo-3 point to the rear of the Priefert and using remote hydraulics to raise/lower a hiller.
The hiller will be a modified back blade that's a bit too light for my tastes - I'll cut it into two 3 footers with the plasma, then build a "double-boom" setup, kinda like two back blades side by side - each one will be capable of angling its blade as needed, I'm visualizing one-pass till/hill with 2' wide raised beds and 2' each side scraped flat. The next pass would give a 4' aisle between 2' beds.
Wife is already drooling over this plan :=)
My old AC 160 has 4 gears slower than 1 mph in the low range, perfect for a really fine seed bed in one pass. I have all the fittings, etc, to add 4 more rear remotes for projects like the above. That's one of those "indoor where it's warm" winter projects for this year :=)
I guess you could say that my interest in a QA setup for the Case is because I know how many things I'll wanna hang on there just "because I can..." Steve