If the tappets are ok just take them apart and clean them out.
Hard to say whether it would be "worth" it with fast road cams, bearing in mind you can't go too mental due to presumably not having pocketed pistons ?
Personally I would just do the exhaust to BD15 profile, a lot change the tappets as a lot easier to do this when changing the cams than a seperate job on it's own later on.
tabetha