55 might be the posted limit for vehicles with a trailer in Cali, but not over here.
55 is posted on the fenders of the tow dolly, printed in a mirror image so you can read it in your rear view mirror. I don't want to get snippy here, but regardless of the shape of the dolly, this whole tow setup sounded questionable. Yes you got it done. But I wouldn't pass this sort of info on as something everyone should attempt... towing a heavy vehicle on a questionable dolly with a questionable tow rig at questionable speeds for significant distances. The Error should always be on the side of safety. Remember we all share the road, and you may not only be endangering yourself, but everybody around you.
Again, you got away with it, so I will end my lecture here.