Notice how many duplicates there are on those pages.
Colonial has three entries and they are the same with very minor differences. Same address, etc. Two are inactive, one is active.
The older listing is mostly alphabetical, but the newer one is quasi-alphabetical as they try to insert new dealers in the approximately correct alphabetical location.

Looks like Yenko bounced between three codes 898, 899, & 900. Why they would do that is a question for a dealer.

Colonial Chev may have changed ownership, that may lead to a different dealer code.

Yenko listed their address as 573-75 W pike St on some documents and on others was listed as 575 W pike St

Yenko Chevrolet and Yenko Sportscars was listed separately on some documents


I don't know if this would have anything to do with the different dealer codes