The JL421 Badonkadonk Land Cruiser/Tank's manufacturers say it fits five, but if you put more than one Jabba-the-Hut-sized passenger in there, I suspect someone's gonna have to walk.
What's more interesting, though, is that even with nearly 300 Amazon review, it took almost seven years for someone to ask the important question:
And now you know. A fully informed tank consumer is a happy tank consumer.
Q: Does the JL421 model have the LATCH system for car seats?
No, the JL421 comes with scatter cushions as standard. You're probably looking for the JX430.
PS the "Customers who looked at this also looked at that" selection on the Badonk is worth a link by itself.
JL421 Badonkadonk Land Cruiser/Tank, made to order, $19,995 [amazon via dt burner nathan]