Paul;
A Generator/Dynamo VReg is not suitable for use with an Alternator...the biggest difference being the Gen VReg must have have a Cut-out Relay through which to pass the Gen output, which is opened when engine is not running, so that the non-running Gen does not become a load on the Battery.
The Alt VReg needs no such Relay and contact as the Rectifiers withing the Alt only allow current to pass one way while it is turning and having an output.
The old VReg, as Derek has mentioned, might still be present, but it is likely only vestigially and just along for the ride...the VReg which is really at work is probably internal to the Alt (this could be verified by studying the Alt and its connections).
See also:
http://www.sw-em.com/Bosch%20Generat...ut-out_contact
Cheers