On a Cougar, what you can use depends on whether it's ATX or MTX.
You need the SVT TB & TB bracket, then either a throttle cable (if it's MTX) or cruise control cable (if it's ATX). Cougar ATX throttle cable is the same as Contour SVT throttle cable.
That's from memory, and I think I'm right
but unfortunately I can't double check it since FastCougar.com (soon to be NewCougar.org) is still down
for the site changeover.
No idea on the ability to use the 3L part.