Brake options for 16” Cragars

I agree with @junkyardhero that, in good condition, the stock brakes (10.87" rotors) would be brakes a-plenty. That's what I'm using on my '68 Valiant's big-bolt swap. My Challenger is another story (or "another 1,000lb." if you prefer) and is getting the big boys.

If you want the larger rotors, you've literally already got the steering knuckles, calipers, hardware, and hoses in that kit--they were on your car the day it was built. All you'd need to upgrade to the 11.75" rotors are the rotors themselves and the matching caliper adapters (slider type). Both are '75-'79 B-body parts (Cordoba, Charger, Magnum) and '79-'81 R-body (St. Regis, Newport, New Yorker). Dr.Diff has the adapters, I believe. Those are essentially non-wearing parts, and everything else except the rotors would be listed for your car at the local parts store. The rotors are available locally too, they're just listed for the above applications rather than your ride.

That being said, you can save $120.00 on the Dr.Diff kit by choosing "subtract knuckles" at the bottom after you've chosen everything else. You've already got those on the car. All the rest would be brandy-new, yet still parts-store friendly come rebuild time.