Long ago I had a 1974 D100 and as I remember the brakes were essentially the same that you would find on a C-Body of similar vintage. The simplest improvement that you could make would be to get some new stock rotors for the front and new drums for the rear. Shop for those on www.rockauto.com and while you are at it get the premium brake pads and shoes. I put on some 15x7 Cop Car wheels with 255/70R15 tires and I never had a problem stopping