You can try the xbox's analog thumbstick for absolute position, but I'm pretty sure you won't like it. The precision needed will probably higher than you can do on the thumbstick. That leaves using the d-pad or analog stick for direction at constant speed control (which I don't like, but you might).
To do the absolute position control, start the game, tab, input (this game), AD Stick X Analog, enter, move thumbstick left or right, wait until mame takes it, repeat for AD Stick Y Analog and up/down. make sure the same thumbstick is not mapped to the "...Inc" and "...Dec" ports. (Repeat, "NOT")
To do the direction at constant speed control, it's almost the same as above, but map the d-pad or thumbstick to the "...Inc" and "...Dec" ports. (which is why you make sure not to map these in the above.)
IMO, mouse, TB, or analog flightstick will give better control for revx, but ... some people love gamepads.