Stock 305 is an area code joke and it tells you where the shop is

The clothing business in the Ultimate list is called Stock 305.

305 is the area code for the real city Vice City is drawn from. It has been used as shorthand for that place in music and on clothing for thirty years, to the point where it functions as a name rather than a number.

So the shop is not just in Vice City, it is a shop that is selling you Vice City. A clothing brand named after the area code is precisely the kind of business that exists on that strip in real life, and naming it that in a bullet list is a joke aimed at about four percent of the people who will read it.