I read the whole thread on the Mega Cab's A/C issues, and because that thread is old, I started a new one. I just bought a Mega Cab last week and I have not had any problems yet, but it has only been in the low 80's so far. Anyway, a possible solution to the A/C problems may be to add an additional or a larger A/C condenser and also put a smaller drive pulley on the A/C compressor. Those two things, in theory, should make the A/C system work better.
I have not seen any posts about the A/C on the 2008 models, so maybe Dodge fixed it already. I can't look at it right now, but I was wondering why I had so many radiators under the hood-two of them were about the same size, so Dodge may have added an additional condenser for the 2008's. I will have to check it out later when I get the truck back. Yes, its at the dealer, but just getting some stuff put on.