Nope.. can't flip it. It'll run backwards. Your best bet would be to sell it and pick up a GM D60. Next option would be to retube it to move the center section.. but that could be kind of pricey.
I read an article once where someone just cut the knuckles off, cut the tubes, bevelled the ends, turned a tight fitting inner sleeve on the lathe, sleeved/rewelded the tubes in place on opposite sides (long/short side) and then rewelded the knuckles in place. Between the inner sleeve and the bevelled joint, the tubes were said to be plenty strong.
I've got another buddy who used an air-arc to blast out the plug welds at the pumpkin (this was on a rear D60) and built himself a simple press to pull the axle tubes out of the housing (seem to remember him saying it took about 30tons of force). He then swapped tubes from side to side and pressed them back in place.