I put one behind my 666hp ZL-1 489 and enjoyed it thoroughly. Mine was 14 lbs. I could take off without even blipping the throttle. It just ate it up. It revved like a short stroke small block all the way to 6800.
It made rev matching way easier.
The compromise, because there are always compromises: It made my tko600 even harder to shift. It would also start to buck 200-300 rpm sooner in a tall gear for the speed.
I'd do it again except behind a t56 and rev it to 7200.
