I have no idea on part numbers, but I do know a little about M/Cs.

The reason the disc mc is bigger is so that as the pads wear and more fluid hangs out in the caliper body the mc doesn't run dry. If you keep an eye on it and top it off once in a while you're good. When you push the caliper's piston back in to fit new pads watch out you don't overflow the mc. A turkey baster or mity-vac does the trick there.

The other thing to watch out for is some M/Cs have little one way 'residual pressure' valves just inside the hard line ports. This is to keep 5 or 10 lbs of pressure in the line to keep from having to pump the brakes when you stop.

Good luck
rdr