18" Wheel help

There really aren’t any “Mopar specific” wheels in anything close to those sizes, just aftermarket wheels with generic center bores. As far as hubs, you won’t do much better for the factory spindles. The DoctorDiff aluminum hubs are basically copies of factory BBP hubs minus the rotors. Baer hubs are very similar. Wilwood hubs have even larger diameter hub snouts.

It’s very wheel specific too. I have Vision Legend 5’s on my Challenger in 17x9”, they have a larger hub bore but even if they had a 73.1mm bore (fairly standard for aftermarket wheels) they’d work fine because they’re quite thick at the mounting face, so the Mopar hub doesn’t protrude. But a lot of wheels are like my RPF’s and are thin there, so the hub has to protrude through the hub bore completely. And some wheels will allow that but then need different wheel caps to cover the hub.

This is a set of the Vision wheels in 18”, they appear to only offer an 18x8.5” in grey but have an 18x9.5” in black. But they offer multiple offsets, so you could run these in the front with a 255

Grey
Vision Wheel 142-8865GM32 Vision American Muscle 142 Legend 5 Series Machined Lip Gunmetal Wheels | Summit Racing

Black
Vision Wheel 142-8865GB20 Vision American Muscle 142 Legend 5 Series Machined Lip Gloss Black Wheels | Summit Racing

and then these in the back

Grey (would have to be a 255, as a 275 needs a 9” wheel in that size)
Vision Wheel 142-8865GM10 Vision American Muscle 142 Legend 5 Series Machined Lip Gunmetal Wheels | Summit Racing

black (would work with a 275 but would need a small spacer)
Vision Wheel 142-8965GB12 Vision American Muscle 142 Legend 5 Series Machined Lip Gloss Black Wheels | Summit Racing

The other thing is, you didn’t mention if you have a Duster/demon/dart sport/barracuda or a Dart/Scamp/valiant. If you don’t have a sport body car you won’t fit 275’s in the back without moving the springs, the Dart/Scamp/Valiants have 1” less room in the quarters.