Probably depends on if you're looking to buy something and drive it, or buy something to build into your daily driver. My kids' car seats take up more room than my wife and I do on the seat, so I'd think 4 across would be a no-go. There are several on 67-72chevytrucks.com that have cut a couple standard cabs up and made extended cabs. Some have cut up Suburbans too, but the roof line is higher and doesn't line up with the rear section of a pickup cab.
