Newby Here BSA B25 StarFire Question?

[bonnietiler]

Hello everyone as you can tell from my name I have in the past been known to have a bike or 2 from the "other" place..I am Bonnie as in the bike that I used to ride ..unless you count a newish 1200 T120..and tiler as in the job that I reluctantly used to do, rather than a Welsh PowerBallad singer of the other chromosome denomination ..I thought that it was REALLY clever when I made it up 20 odd years ago..Times winged chariot etc etc. So, I have bought a matching number BSA B25 Starfire as t was similar to the one that was my very first bike  I owned back in the very early 1970's.
It is prefixed BD, first question does this make it a 1970 model year and if so where is my Oil pressure switch, should I have one?...I have a warning light within the headlight shell..unconnected, but am failing to spot my switch. The previous owner was erm..enthusiastic (Torchy I shall now call him) I particularly like his domestic electric connection blocks that he incorporated, ho hum...so given that he has er..experimented with his wiring preferring uninsulated connections throughout..do I need a particular wiring harness for a 1970 model or will a 1969 do?
Many thanks in anticipation