Usually only ever 3 shanked threaded screws hold the NORMMALLY.. radiator support and mounted regulator in place.

NOT ORDINARY SCREWS..

REMEMBER or be aware.... this era regular has  INSULATED MOUNTINGS....for a reason.. so don't do what a few people have done & fasten them metal to metal onto the radiator support panel.. then FRY the regulator and carry on about it being faulty.. cause it certainly will be untill its replaced and done properly....!

External regulators are NOT used on cars with an Alternator that has an internal regulator.