If there's the slighted chance you will get a TC then a 3500 long bed is a minimum. It's actually kind of silly that 2500 series trucks even exist since 3500 SRW is available. There is NO reason to get a 2500 instead of a 3500.
I can't stand short beds. A long bed truck isn't really big enough. Bikes, tools, grill, firewood, generator, chairs, cooler, etc. adds up quick.
I would get a gas truck for your use. Diesels are nice for lots of power but you're not talking about doing anything that requires lots of power. I test drove a 2015 Ram with the 6.4 Hemi and I really liked it. I've heard nothing bad at all about that engine. That would be my choice for a gas truck right now.
