Which old MM should I buy for my new backhoe?

I got a great deal on a CASE 762 backhoe from an 860.
It weighs 2,200 lb.
It wants 13 gpm, but the pressure is not stated

I welded up an adapter for my Jet Star and it worked, but was too heavy even with counterweights in the front. I also think that most hydraulic systems of 860 era wanted 2500 psi which is twice what the aux. pump on my Jet Star provides.

So the bad news, and the good news, is that I need to purchase another MM!

I assume that none of the old MMs provided over 1500 psi, so I will need to build my own pump for PTO or pulley drive.

So, how much should my larger tractor weigh? Is the M5 or GB (2000 lb heavier than my Jet Star) big enough, or do I need something bigger?

Is there any reason to get a 3-pt hitch? It is easier to weld an adapter for the axle and drawbar.

Any advantage of belt drive over splined PTO?

I assume that a GB without a 3-pt will cost less than a M5 as its application is limited?

I actually like the idea of having a pully as I have a machine-shop full of old line-shaft lathes and mills which were converted to electric drive, and I could use the MM to drive the line-shaft so that I could convert them back to belt-drive (until I find a steam-engine)

My big Mo 600 has 13 ft backhoe. Also my Jetstar 3 industrial has 23 gpm side pump like Big Mo. My Motrac crawlers also have big
pumps. Most mounted where belt pulley is. All are Jetstar based. GB never had 3pt. Jd 4020 in early 60's would be first to go over
2000 psi.

My Jet Star also has the PTO driven aux. pump on the left of the driver, but the pressure of 1500 psi is low for my backhoe.
So:
can I shim the pressure relief to pursue over 2000 psi?
Are alternative pumps available which bolt up and support higher pressure?

Is the fact that the GB never had a p-point an advantage with the backhoe?

How hard is it to adjust to the hand-clutch of the GB (can an old dog learn new tricks?)

MM used volume and less pressure like most 50's product and ran lower rpm. No U/G ever had 3 pt. 335.445.5 Star first in 1957. GB
clutch is adjustable. Is a Twin Disc clutch. Pull pin on clutch and rotate collar CW to get good snap on lever.(Through hand hole)
My Motrac will easily lift 3500 lbs. Big Mo backhoe bit slow but lots of power as both have huge cylinders.

I dont know anything about hydraulic systems on
Any of the mms , but as far as mounting a backhoe,
A GB would be inconvenient in mu opinion to have one
, just because of how you have to get on
the tractor, from the back. An M5 or basically
5 star or newer row crop tractor you get on from
The front, and thatd be easier