A quick search showed units between about $300 and $1,300. But I found nothing specific to the Challenger.
Goodyear F1 Supercar Summer Performance tires about $450 for 4 at Tirerack.
Bilstein shock/strut about $115.00 each
So with our a firm price for the steering mod, let's say at the low end, $350.00.
You are looking at around $1,200? That does not include shipping or installation. This is very rough, but may give you some idea. You will likely need other parts to complete the install too, though I am no expert. Others here will know. You could also contact your mechanic to ask them.