The Lionel TPC is the perfect controller for Williams trains. You can start out at 30% power and multiple units will start up synchronized with each other.
Any transformer/controller that starts around zero to three volts will do the job just fine without rewiring the motors, but may not start multiple unit diesels in sync.
In my opinion, it's about getting a good controller, not modifying the locos, and that is the opposite opinion of some others.
