I just scored on a 3557K012CR in new condition.
I once again took out the stock 6440 RPM Buhler motor and swapped it in with the 5300 RPM 3557K012CR.
On my test drag strip track at home, which is 11'-4" in length on carpet, I did average runs from start/finish with the stock motor in 1st, 2nd, 3rd gear and 3rd gear with 1 gallon water in bed.
I then swapped motors and did the same average runs.
Results:
1st gear, the Buhler motor finished faster by 3.0 seconds.
2nd gear, the Buhler motor finished faster by 1.0 second.
3rd gear, the Buhler motor is the same speed as 3557k012CR.
3rd gear with 1 gallon water in bed, the 3557k012CR is faster by 0.10 second.
Conclusion:
On flat grounds with no load, the Buhler motor has a higher top speed in 1st and 2nd gear, but in 3rd gear both motors were equal in speed.
Where the 3557k012CR shines is when load is introduced. In 3rd gear with or w/out the 1 gallon water, the speed was identical and did not change.
Whereas the Buhler motor slowed down significantly when I added the 1 gallon water.
I can definitely feel the extra torque from the 3557k012cr and will spend more time in 2nd and 3rd gear whereas the Buhler was only 1st and 2nd.
