Alternator models with integral diode. (most common)
Disconnect the brown lead and the thin black lead from Regulator box, terminals 51and 67 respectively and tape up (these are the old wires from Dynamo)
The old wires from the Dynamo (at RHS front) need to be taped up and secured out of the way
If your alternator comes with the loom then connect the thicker brown wire to terminal 30 of the regulator box
Connect the thin black/Mauve cable to the terminal 51 to join the green wire or use a connector block.
If your alternator comes without wires then you will need a new length of thick brown wire (35 amp) and connect as above, plus you will need a new thin wire as above, OR you can use the old thin black Dynamo wire if that suits.
Note: When you fit an alternator, the regulator box no longer functions, but just used as a connector point! You can remove the box completely and just use connector blocks if that suits.