Registered. It depends on the offset of the wheels and how wide you have your tires, with 9.5" id run at least a 275 tire and you should clear just fine.

Can you put hellcat rims on a RT?

There's no reason they won't fit. Hellcat wheel is a 20x9. 5 with a +18 offset so really not a lot of difference than a 20x10 TorqThrust which is also +18. You'll have the same size limitations on the front, with a 275/40r20 being about the max you can fit.

What is the hellcat lug pattern?

Bolt pattern: 5x115. Offset: 15 to 22 mm.