I don't see why your "swing under" idea won't work, as long as your current panel is attached to the machine really well, and can support the weight of two wheels mounted in enclosures, and can handle the stress when those enclosures are swung up or down. I've got some Off Road wheels here, and if memory serves, they don't protrude very far inside the panel. I'll try to dig 'em out and get you some pictures, and weigh 'em, too.
Pedals are easier- Happ sells a model that's made to bolt to the front of the cab. Or, if you get the kind that mount to a board on the floor, that's easy too, as it's just a board, on the floor. I'll grab a pic of my Off-Road cab's pedal setup, too.
As for how to interface 'em, you can do two wheels on one mouse hack, or a whole bunch of 'em on an Opti-Pac. Pedals can be done with a Dual Strike hack, or Dave's AKI interface.