I upgraded my stock size to Duratracs in 285/75r18 and still have the OE wheels. That's more of a 11.25" width tire and not a 12.5". Mathematically that size tire gives out to 34.8", but Goodyear says it's actually a 35.1" tire. I get a little rub on lock, but I haven't installed spacers yet nor a leveling kit. I actually have both in the garage, but been busy. I did initially rub on the mud flaps, so I replaced those with the mud flap delete kit from McGaughy's. That's about $125. I've been told Rough Country makes a mud flap delete kit for about $65.
The advice about leveling kits and recommendations to buy use 4Auto. That's coming from every leveling kit manufacturer. I spoke to ReadyLift and they told me there's a noise with 4Auto. They haven't looked into what the noise is, and won't. They're just covering their butts. Not every truck makes the noise, and some people have said they don't hear the noise. 4 Hi and 4 Lo are not affected.
Pulsar LT is around $600, iirc. If you're only interested in calibrating your speedo, Rough Country to the rescue again, and for several hundred dollars cheaper. I had no desire to do any of the other stuff the Pulsar LT does, so it was one of those rare situations where Rough Country won out. There gave also been issues with the Pulsar when it came to getting the truck serviced. Lonestar Hawaiian did a video on that, too.
As for the noise from the Duratracs, it actually goes away over time. I wrote my original one to 50,000 miles. They weren't bald, but were low on tread life. At that point they were silent.
Biggest reason I got Duratracs and not another tire was weight. The 35s I got are only 10 lbs heavier than the OE Duratrac size, and the 35s are E-rated. Many other tires are a bit heavier. Rotational mass and unsprung weight can add up to issues. Speaking of E-rated tires, these Duratracs corner better because of the stiffer sidewall. However, they ride a little bit more rough, too.
I'm no expert, but I'm willing to share what little knowledge I have. Just ask if you have any questions.