Stepper Motor size

I'm looking for stepper motors for my second CNC mill. My Bridgeport
Series 1 has LARGE steppers. I don't have the specs. but I guess at
least 2000 oz/in.

My second mill is a full size bridgeport type knee mill which needs a
CNC upgrade. I'm using Ahha Artisan FWIW. The control uses 48 volts
and needs 8 pole motors.

Anyway, I'm looking for large steppers and can't find any. My first
question is what size do I really need? I do the conversion from
oz/in to foot pounds and steppers seem really puny. For example, 540
Oz/in. = 2.8 foot pounds. A typical power feed is 35 to 70 foot
pounds.

Anyone have a source for large steppers? Preferrably used, or at
least inexpensive.

Karl