guy tells me it takes 40HP to run the tiller
Tillers do use a lot of PTO HP compared to some other implements, especially if your soil conditions are clay or in any way heavy. Still a 60" tiller should run fine on 30PTO HP even in heavy soil. That is giving 5PTO HP per foot of tiller. I run a 50" on my little New Holland with 18PTO HP and when things get really hard I will run it on the bigger Kubota with 23PTO HP. But on the New Holland I'm running slightly more 4PTO HP per foot of tiller while the Kubota, with almost 6 PTO HP never slows down in heavy soil.
A reverse tine tiller, that spins 'backwards' will use more PTO HP than a forward tine tiller.
A spade tipped tiller, like on some of the Howard Rotovators and similar uber premium market grade brands, will use more PTO HP than an "S" or "L" shaped tine.
IF you really can get parts for it, it is a hell of a deal.
The downside is you will be running your tractor over tilled soil while you make your second and each consecutive pass, so you will be compacting the ground that you just tilled. That is sort of pointless! And that is why, when you get a tiller that is narrower than the width of the tractor you need to get one that has the OFFSET feature so you can run it without driving over your freshly tilled soil.
I think I would pass, largely because of the small size relative to your tractor and the lack of OFFSET feature. If it had the offset, it would probably be worth a try.
BTW, make sure the 40HP the guy claims is not the MAXIMUM HP the gearbox can handle. If it is, you will chew up the tiller!
I think I'll go look at it . The guy has a 30plus hp Masey
If that is an ANTIQUE gas powered Massey then it is likely that it puts out a lot less HP than is stamped on the engine.