The Felder's motor actually runs at the same speed as US-made motors as an induction motor's speed depends on line frequency and all induction motors with the same number of poles will run at about the same speed. The difference is that Felder had the sheaves sized for a motor that ran 20% slower than you are currently running it, so you are getting a speed increase due to the sheave ratio diameter being different than if it were designed to be sold in 60 Hz land.
Look at 3 phase motors. If you use one of them, you can also use a VFD to very easily get speed control. Hooking up a VFD to a 3 phase motor is trivial to do. 3 phase motors have the same frame and shaft sizes as single phase motors so one would be a direct bolt in. A treadmill motor will be difficult to adapt into the motor mount and you will also have to get a speed control for it as well as you will be unlikely to be able to use a treadmill PCB to do it and have it work well.
Art,
No expert here. All I know is what Felder told me, back in '99. My saw was 3 phase with a built in converter that enabled it to run on single phase.
I got it that way to have VS on the shaper motor, and didn't even know it worked on the saw motor until I got it.
Rick Potter
DIY journeyman,
FWW wannabe.
AKA Village Idiot.