-I saw your request for suggestions on switching over from air to electric wipers but didn't respond right away because I was knee deep in swapping mine at the time and I didn't know if it would work or not. My right side air for my GM needed rebuilt, the only quote I got was 400 bucks that seemed to be better spent on a different plan. My father had a 1990 E-One fire engine that he bought for parts, so i stole the motors, hardware and switches to see if I could make them work on my 4108.
-It took me 3 hours to get the parts out of the fire truck so I wasn't too hopeful. But when I got home, I couldn't believe it. I pulled off the fiberglass cowl and held the wipers in position outside the bus. After checking the arc of the blade, I marked the windshield with a sharpie marker, then went inside the dash and measured down to where the motor shaft should be positioned. I only had to move one copper air line to make room for the new motor, and it was for the air operated control. I drilled 3 holes and installed it in 45 minutes. The bus is 24v, so I grabbed a spare 12v battery and hot wired the wiper. Worked like a charm.
-I did the same for the driver's side, but it was behind the dash so space was a little bit tight. I repeated the process, and had both motors and wiper arms installed in less time than it took me to remove the old ones. Obviously, I have some wiring to do to finish the job. I already have a 30amp 24v to12v converter that will run one, or maybe both. The firetuck wipers are 18", but I spaced them to accommodate 22" blades which will cover pretty well. I suggest solving your problem the creative way. Not sure what your MCI dash looks like but maybe start by looking there.