I would say the engine is a wisc. and the rear end sears had used some like them. I'm can't remerber if sears used wisc engines.
God moss didn't take you long to find that, you must be older then me.
Not a bad looking moto-mower model 6020.
Probably 1965-66. Easy to guess if you can read the date code on the motor.
The motor appears to be original (I'm reading this on a laptop). A 6HP B&S.
The hood is missing as well as the plate that was welded to the steering column where the back of the hood would have latched.
The plate was where you have found the model number.