It's been a while since I started this thread when our need to replace both air conditioners surfaced. Well at the time I managed to get one of the units to work so we postponed buying anything. Fast forward to this spring and before I started dismantling the 345 I tested both of it's air conditioners and they worked great.
So, instead of buying new units I parked the 310 right next to the 345, bought a couple of 2x10's and laid them across the roofs between the two units. I then procceded to remove the front air conditioner from the 310, slide it across to the 345 and then basically just pushed it off onto the ground. I then removed the front air conditioner from the 345, slid it across on the 2x10's and installed it on the 310.
Repeated the process for the rear air conditioner and bingo, working A/C on the 310
I'm sure I only postponed the need for new units on the 310 for a year or three but that means the money can be used for higher priority items.