TTS toolholders are 1.5" across at the widest point.
They should fit fine, assuming that's an R8 spindle You may need to mount a lathe tool in a vise and take a light facing cut across the spindle. TTS relies on that face for contact, but in most situations, it's not a contact surface. So on some mills, it's not smooth and free of runout. I can see one dent on your spindle near the face, so you should plan for this possiblity.