I'd be looking at changing those hubs if it was mine. Re drilling from 4 bolt to 5 bolt is a little dangerous. If you have a look at some of the wheel studs the holes are overlapping slightly with the 4 bolt holes. This really weakens the hub.
If you upgrade the brakes buy some new blank hubs and get them drilled properly. There may even be an off the shelf kit available.
Have fun with it.
