Aftermarket brakes for a 70 Dart?

Wilwood is just high cost for mediocre performance. Their 4 piston kits provide less brake force than a set of the 11.75” Mopar rotors with the later 2.75” piston calipers.

Given your stated goals, I’d go to DoctorDiff and pick up a Stage II kit. I ran that brake kit on my ‘72 Challenger for 70k+ miles, a lot of it with 275/40/17’s up front. They work very well and even larger brake kits that require larger diameter wheels are only incrementally better. If you’re keeping the 15” rims the 11.75” set up is about as big as you can go.

Mopar 11.75" Front Disc Brake Kit (Stage 2)