You might try Redmond and Sons for parts. http://www.redmondmachinery.com
They used to service a lot of schools and I've had some luck finding Delta Rockwell parts from them when eBay didn't work.
The pulley on the bottom of the motor is for the power feed attachment.
You might find this page...
Just to let you know if you are still looking for the manual we have it on our site here:
BOICE CRANE 3500 10" Monomaster Table Saw Instructions & Parts Manual
As for the knob, I'm not sure where to get Boice Crane parts other than eBay. The manual would could help you get the original one...