on our 2 Massey's i have replaced alot of woble boxes over the years. The problem is that they get loose and you dont know it untill it's too late. they dont have any adjustments they are either good or shot. I have modified the headers to accept an IHC wobble box. they are of open design with tapered bearings so they can be adjusted to get rid of the desasterous slack. they cost about $800 instead of $1500 or so. I have used these for about 5 years trouble free. If you would like more info on this mod let me know.