Correct Disc Brake Caliper for 68’ Dart

Your vehicle was converted to the large bolt pattern, disc brakes (4 1/2 inch bolt pattern)
You most likely have 73-76 A body disc brakes.
Original disc brakes on a 65-72 A body car would be the 4 piston caliper, Kelsey Hayes system, disc brakes.

This is what's original for your car, if it's an original disc brake car, or converted over from drum brakes.

You can fix your problem by reversing the spindles, and calipers side to side, having them face rearward.
Then you will need to use "F" body hoses, or 69 Camaro hoses.

Kelsey Hayes A Body Brakes 2014 001 (Copy).JPG