I think you're right on target with prioritizing the sliders over the bumper for now, if you must choose. Also, I'd recommend waiting on the bumper until you can get the winch too. Now, for the gen 2.5, I think you'll need a small amount of fabrication done to get the ARB bumper to fit.
RogerH on here has this same model and he can fill you in on what's required. I can tell you that whoever did the work for him made it fit perfectly. Wil at
Sierra Expeditions can help you sort out which bumper you need. (He's the one Roger ordered from.)
I think you're really going to like this truck. I haven't even seen pictures and I'm already happy for you. 3.5L engine, rear locker, expo white...just add sliders and a fridge and you're all done
As for tires, where do you plan on taking it? Are you thinking an MT or an AT tire? I think you have a ton of options to go with. The new Goodyear MTR is a good all-around choice, but then there's the BFG ATs or KM2s, or the Maxxis Bighorns, or the Cooper STTs, or the...or the..., and so on.