I want to upgrade the brakes on my 72 bronco. I would like to do it in a couple stages and do the booster first and then later put front disc brakes on. Is this booster compatible with both drum and disc brakes? Thanks!

Yes, it is compatible with all drum brakes, disc and drum or 4 wheel disc brakes. People will normally do a disc brake conversion first, for better and more consistent front braking. The power brake kit does not have a requirement other than 18 in. of manifold vacuum to operate properly.