White vans are a GTA constant, and the Bravado Rumpo is the longest-serving of them, present in every mainline game since GTA III. It shows up in GTA 6 through Trailer 1 and screenshots, still wearing Ford E-Series proportions. Files list four seats, 2,500 kg and rear-wheel drive, all datamined. Expect a plain, practical box that nobody looks at twice, which is rather the point.
Rockstar has not confirmed how the Rumpo is obtained, but a delivery van this common will almost certainly be all over Vice City's streets from day one. Finding one should be trivial; that is expectation, not announcement.
The community companion for Grand Theft Auto VI. Database, maps, guides and tools for Vice City and the state of Leonida.