just been to mnr racing and he does all the rear wish bone set but i dont know how to go about building the chassis around the diff for the pick ups
has any one used these wish bones and could they help

Why not ask MNR for the dimensions of their rear box

I think MNR sell Diff mounting Plates ready cut to size that you weld to the chassis.

He is asking for the rear suspension box dimensions, not the diff mounting plate. I got the impression he's trying to figure out how to attach the wishbones t the chassis.

seeing as I am feeling rather "to the point" this evening, if you have to ask the question, maybe you would be better buying a complete chassis from MNR!!