For my 67 390, first degrease it. Then sandblast or glass bead it if not to bad.
Mine had factory yellow paint dab which I put back. I painted my bell housing with Eastwoods Cast Metal gray. Then some research states Ford had blue engine overspray paint on area bolting to engine.
Try not to sandblast it. Heres why: It leaves a "sandblast patina" to the part. Try to clean it with a degreaser paying attention to any inspection marks so you can replicate those after you clean it all off. And remember to take photos of those marks, it might be important in the future.
If it is cast iron, you might want to clear coat it, just don't use the glossy clear coat.