Thanks for starting this thread, Chuck! My girlfriend and I have been looking at getting a vehicle to support our summer and winter climbing outings, and we have been converging on a similar answer: pre-07 Ram 2500 diesel with a FWC popup. Like you, I'm not set on this, but it's looking pretty good.
Here are a few things I have noted:
First, I'm a tall guy (6'4") and was a bit surprised by the Dodge extended cab. I could, in a pinch, sit behind myself. I wouldn't want to do it forever, but it works. My girlfriend will have her seat up a bit, so there's even more room behind her. With the seat up, too, we could easily fit 4-6 large Rubbermaid bins full of stuff. For us, crew cab is not a requirement. If you haven't already, go sit in a few and see for yourself. Interestingly, with the manual, I think you may lose the ability to put someone in the middle of the front seat. That may be a concern given you extra passengers. Again, go check it out for yourself.
Along those lines, I was a bit shocked by how roomy the FWC Hawk was. I had been assuming 8' bed w/ Granby until we got a chance to go by the FWC showroom in Sac. Again, it's just two of us, but the Hawk is plenty. It would be tight, but I don't think it's out of the question to fit two small kids in the 2nd bed, too. Maybe I'm naive, but I feel like the difference between the 6.5' bed and 8' bed is huge in terms of a DD, parking, maneuverability, etc. Like the cab, if you haven't already, find a FWC (or better yet, go to the showroom) and test a few models out.
In terms of storage, too, don't forget the FWC roof. As climbers, we carry a ton of gear, and the plan is to put the bulk of it on top of the FWC (Thule box, ski racks, etc.). FWC offers lift assist options (gas and manual) to help you get the roof up with a few hundred pounds on it. There are some obvious downsides (clearance and the difficulty of getting to stuff with the roof popped), but it feels like the only way we can make the 6.5' bed work due to the decreased storage space. This definitely strengthens the argument for the 3/4 ton (over 1/2 ton), though.
Finally, have been going back and forth between gas and diesel, largely due to concerns about getting stuck after a cold night in the winter. We have discovered that there are a lot of aftermarket solutions, though (thanks to another thread on this site), so the latest thinking is just to experiment with the stock setup in CO this winter and see how burly of a solution we need to add.
I'm not set on any of this, though. I'm entirely open to any insight from people that have more experience with this stuff.