One of the reviews on that box indicates the inlet connector is CS6364. Parks would have NEMA 14-50 connectors.
As roach711 indicated, there are good reasons to have the ac ground connected to the bus body. I'm not familiar with any good reason for avoiding
having the ac ground and the dc negative both connected to the body -- it's generally assumed those connections would both exist, in fact.
Good cords with a few power strips for ac distribution isn't a bad idea. But when I write "good cords" what I have in mind isn't on the shelf at any big box. I'd use the SOOW type cable which has a very thick black rubber insulation (it's about 3/32, almost 1/8 inch). The thinner insulated stuff at home centers, even the "heavy duty" types, may tear open surprisingly easily. The SOOW isn't terrible in price: Home Depot currently offers a 25' roll of 12/3
for $33.21 online. That'd be enough cord to drop an outlet within 8 feet of each end of a 40 foot bus and another one or more in the middle.