I've locked this board so it is available for reference only. The active forum for the site can be found here: http://vsgt.aforumfree.com/index.htm
I was given a 1966 custom 6 It needs a belt that goes from the motor to the blades
The original belt part number for a 1966, 36 inch rotary mower attachment, model number 917.99620 is 5600H.
Use the cross refernce belt size chart, should be a common item, readily available locally.