http://www.fennerdrives.com/powertwist-plus/
These work pretty good. especially on the slow running old engines. adjust tension normally.
if you wish to replace with OEM then you will need to separate the drive coupling from the front engine pulley then install the new belt
No, you do not. The coupler separates by taking the six bolts off and driving a chisel between them to slide it back. Use the Google search function in the upper right corner. There was a post on this a couple of years ago.