I bought this exact setup for my B6000 and had no problems hooking it up. I did drill a hole closer to the tractor which I used for the lift linkage but I think it would have worked if I turned them upside down and around the check chains. That same site eezs.com also has different kits.
Maybe I am not understanding your hitch setup....but have you tried the inserts to change the size hole in the arms and top link you have now to the smaller pin size cat I? If that is what you are asking those things are cheap, A buck a piece, you would need 3. Maybe I am not understanding what you have now????
Or.... are the arms you have now too wide? If so I had a M4900 that I had to reverse the arms and also use the inserts in order to use a chinese made roto tiller.