My Barracuda keeps them on at 7,000rpm powershifting a 4-speed. I have A/C and P/S, running the 70-newer bracket setup. It was quite a challenge getting the pulley alignment perfect and choosing the correct belts. As stated, there always seems to be one belt that is a touch longer than the other one, but on a 2 belt A/C compressor, alignment comes into play and solves that problem