[Guy]

Jim, reading between the lines, I am guessing you are thinking about rebulding a transfer switch that has an old Cutler Hammer contactor ? Not much can fail in those contactors, other than the contacts or contol coil Parts are still available. Each contactor  has one control coil and 3 moveable contacts, 3 stationary contacts and 3 springs.   Verify the operating voltage of the coil, probably 120 volts, and you are ready to buy your repair parts. Often, replacement parts cost more than upgrading to a current model of contactor. Your contactor is rated at 65 amps and 480 volts.
Lanco Contact Company
Denton Texas
877 799-6545

Good luck