I've just been looking at the wiring, your going for the negative earth system/connections, it makes it easier to add modern items.
The connections from the alternator to the rectifier/reg look OK to give full out put all the time.
The connections from the rec/reg. to the earth and ammeter look OK.
And the connections at the other side ie. contact breakers look OK apart from the Black/white wire which goes back to the ignition switch ( 15 ), I know this is as the original wiring but I don't know if it will operate with the Wassel rec/reg. I think this is for the emergency start .
I also don't know if the connection between the light switch and ignition switch is needed, it may be OK . I've added a Boyer ignition to my Leader with the Boyer power box and retained the original wiring and apart from connecting the two units into the wiring , the connections are as standard and it works OK.
I've not checked the lighting switch/components wiring but if its as per the original apart from the negative earth it should be OK. I've done exactly the same on my 270 Leader -- neg earth but the same layout and it's OK.
Brian H. PS I've come across alternators with wires which have been altered re colour of wires, which can cause problems until you find out which is which. It may be best to get someone elses comments on the set up/wiring.