I have a Beta25 e/w the upgraded 70A alternator. Is there a smart regulator available that will mate with this alternator, or if not, what modifications are required?
Yes an external regulator is available for the 70 amp alternator, we use on made by Adverc. Most alternators will need a modification to allow and external regulator to control the field winding of the alternator.
I'm afraid I have no experience with the other regulators you mentioned. The Adverc we know to work well and does not require the existing regulator in the alternator to be isolated or removed. This means that in the event of a failure you will still be able to charge your batteries, albeit at a lower rate of charge.