Any suggestions?
Attach it to the wall so you don't knock it over.

Use analog pedals if at all possible. It makes a difference on some games, especially pole position where you lose time if your tires spin during acceleration.
Use original ones or repurpose some from a PC driving setup if you can find them cheap. You'd probably use an A-PAC or U-HID to interface them although a lot of the newer ones use 10k pots which theoretically might work with a hacked gamepad. You could also just build your own with cheap radioshack potentiometers if you have the skills.
If it's an old PC with a gameport, you can wire 100k pots straight to it with no other interface.
Since it's a small cab, you might want to have them separate and on cables so you can straddle the cab while playing.
By default MAME uses a toggle button for shifting. I'd much rather have an actual Hi/Low shifter. See the MAME section of the driving cab info thread stickied in the driving cab suforum for how to make MAME play better with one. All they are is a lever that presses a switch when it's in one of the positions. They only had one switch in them. The game assumes you're in the other gear if the switch isn't closed.
You shouldn't really need much else for those games. Maybe a turbo boost button for Ivan Stewart's Off Road.