Alternators are self regulating so do not require a voltage control box.
You are able to keep the control box by either bypassing it or using it as a junction point; or you can fit one of these dummy control boxes with the wiring modifications and fitted with a 40-amp fuse.
This fuse is highly recommended, giving protection to your electrical system while keeping the original appearance to the Healey’s bulkhead.
For alternator conversion
This is a list of alternate part numbers you can use to cross-reference for your Austin Healey
APP # BN1-BJ7
AH # ELG267
OE # na
Quantity per vehicle = 1 w/ alternator conversion