My choice of tensioner is the one from member TurboBuick1 --- you can check it out in my album. Gots lots of miles on mine with zero issues. Here's the link....
http://www.ebay.com/itm/49-66-80cc-...ensioner-Spring-Loaded-Michigan-/181196082385
Best of luck in your project!
I'll second that. I also use theTurbobuick tensioner along with Mapbikes Cut Rollers. See pic here.
http://motorbicycling.com/album.php?albumid=1499&pictureid=10745
Nice and solid with good adjustment.