Funny, because I've recommended (in print) that they should be done on a flat surface for Achilles insertion injuries. But that's not what I did. I did the full drop. And it worked spectacularly well. Again, though, I quit running while I was rehabbing--although that wasn't that much of a sacrifice, given that I couldn't do track workouts, fast reps on the roads or trails, or tempo runs anymore. And I couldn't even run for more than 1-2 miles of distance without stopping to ease the pain. Basically, I couldn't run at all. So quitting was going to happen with or without the rehab.
Other strengthening was basic: Squats, step-ups, single-leg deadlifts, step-downs, side steps (with resistance band), monster walk (with resistance band), hip adduction (with resistance band), etc. FYI, I did lunges at first, but took them out of the routine due to concern about injury--at age 53-54 (55 now), I felt like my reduced range of motion created an injury risk.
Once I started running again, I also included a weekly session of technique drills (skipping, high skipping, long skipping, flat-footed marching, high knees, bounding, quick feet, quick hops, and butt kicks, all alternating with strides), in order to help rewire my nervous system to use all the improved strength/range of motion in my running stride.