I will just throw in my 2 cents, since I have been looking at trucks and am also in N CA. ( Bay area ).
Most people on this forum know 10x more than I ever will about trucks than I do, but living in CA always means that we have to think about the next 5 - 10 years of the nutcase / diesel haters in Sacramento. They are making it harder and harder to own a diesel - and inconvenient. At least some of the users now have to go in for an emission / inspection every 6 months vs every 2 years like before, so a complete pain.
For my own use, a 3500 SRW megacab is very close to my needs.
When I look at the cummins 6.7 option, the engine / transmission combo removes about 1 000 lbs of total payload, mostly in the front of course.
When I compared the DRW to SRW, by the time, by the time the additional axle and tire weight is added on, it didn't really help as much as I thought in terms of carrying capacity. Especially for use on soft ground or icy roads, the searching that I did - seemed like it was better to have wide SRW vs the narrow DRW tires. Again - just my searching - no personal experience.
There are a lot of discussions on line about Cummins plan to release a modified version of the 6.7 engine so that they can configure it ( factory ) for diesel, gasoline or something else - maybe propane. Along with it, there are people at Cummins talking about their efforts to trim off some weight from the new engine + trans combo that will come with it.
I don't know anything other than what is being posted by leakers and speculators, but it kind of makes sense and they have already done this for their larger engines.
A big part of the truck market looks a lot like service body truck fleets, and those fleets don't want to deal with CA government diesel hate problems, so we are all kind of playing along.