I would still opt for obtaining a manual from Electro-Arc, they used to be good to deal with at one time.
They used to give all manuals/schematics.
The OP states the Bodine motor is 120vdc, Bodine make a wide range from 12v to 230vdc.

 

At full voltage and a reasonable load a motor will be running close to it's rated speed, which is probably way faster than the disintegrator can do it's thing. So some speed control will be needed. The actual speed range is not given and so I can't provide advice there. But I did recently run that winch on 12 volts while the tag on the motor said 120 VAC. Something is wrong there because it is a PMDC motor. This is a very custom winch for a very non-standard application.

 

At full voltage and a reasonable load a motor will be running close to it's rated speed, which is probably way faster than the disintegrator can do it's thing.
So some speed control will be needed.

Hence the PCT board mounted right next to the motor!! ?

Usually the motor control is not too exotic on these machines, not from the ones I have worked on. (It's been a while).

 

I am wondering if a triac light dimmer followed by a bridge rectifier would work. That is as simple as I can imagine it being.
The reversing switch would be after the bridge rectifier.

 

I knew there was more to this system than just a variable speed motor but I did not know exactly what. Thanks!

Do you have the model of the M/C? I could look through and see if I still have info on the one's I re-built.

 

Can you trace out the schematic of the plug in circuit board. I think this board controls the motor.

Les.