Well the Major System converts numbers into words and maybe sentences (Kim Peek had a great memory for Sentences) and in the Mnemonic Major System not only the same things are done but also the the words are converted into images (Who I think Kim Peek had a great memory for) and I think that if the Mnemonic Major System in used with the Journey or the Memory Palace System by a Peson who has passed The Knowledge(And thus has a good or great memory for locations) then the recall of that person will be even better and his speed of recall will improve by double if he uses a Dual Mapped Memory Palace,
Cheers.