4 speed Casa close ratio gearbox

Looking at getting a 4 speed close ratio gearbox over the winter (can't run to a 5 speed cost wise). Contacted AF Rayspeed about their close ratio gearbox, but they had loose gears only no gear cluster/Xmas tree and they weren't sure when they would be coming in . I know there are "versions" available on certain auction sites, but I would rather buy from a reputable dealer who has developed/tested and put the time and effort into a product.
So I'm looking at the 4 speed casa close ratio gearbox, any feedback please, longevity .My current top end is a Avanti 225, EX-box clubman and LI150 gearbox 16X47.Appreciate your help
So I'm looking at the 4 speed casa close ratio gearbox, any feedback please, longevity .My current top end is a Avanti 225, EX-box clubman and LI150 gearbox 16X47.Appreciate your help