which spindle motor will work

It says K1 and K2 are the tacho signal ie a DC voltage proportional to speed. I doubt that will be any use with modern drives.

I have similar SEM motors on my Shizuoka mill with Centroid Acorn controller and drive them with a CNCdrive.com driver. However, these use step/dir for position control so wouldn't be much use to you https://cncdrive.com/downloads/DG4S_series_manual.pdf

I suspect you might be better off using a modern servo drive that takes a direct (isolated) 0-10V analogue signal among other optional inputs. They can usually be configured for speed or position control. I have used Yaskawa servos previously but also Lichuan servos as suggested by Jazz, which are more cost effective.

its controlled by Mach 3 via a uc400eth motion controller from memory i bought the Breakout board CP0-10V CNC 4 Axis with Charge Pump and Relay
Product Code: CP0-10V which supplies the 0-10v
from cnc 4 you
ive had this machine a very long time and changed the spindle motor years ago so my memory of the original performance may be confused but i changed it for a reason even if i cant remember it .
im 90% working with aluminium , cant afford a haas minimill ,so just trying to make the triac the best i can . if everyone else is getting on well with the 4000rpm dc motor where the torque seems to drop off rapidly from 1500rpm the issue might be with me.. as always advice/guidance is welcome