Which wiring harness would you recommend I go to. Looking for something maybe more straightforward. And you are right ….zero experience with British bikes. You mention the green from timing side. I don’t see a green wire in harness or controls.
The turn signals, if standard have a green wire. If later after-market or even later Genuine LUCAS have a black wire.
We should start with what you want to accomplish. That you say it's a 1970 doesn't say as much as you might think. A picture of the both sides of the bike and of the headlight would help. Besides 1970 being a transition year, people often change parts more-or-less like you're trying to do.
You want turn signals - we know that.
Do you have a switch in your drive-side side panel? If so, is that a 2, 3, or 4 position switch? If not, then where is the main bike switch and how many positions does it have.
You said you have an ammeter. How many warning lights are there in the headlight and is there a switch in the top of the headlight?
Do you have an oil tank on the timing side or a box-like oil tank in the middle?
Are you planning to stay with points?
Are you planning to stay with a bridge rectifier and Zener diode?
Are you planning to use Sparx switch consoles on both sides?
If someone asked me to wire a bike with turn signals, I would likely replace the headlight and eliminate the ammeter, have three warning lights, and change the master switch to a 3/4 position switch - basically wire is like 72-74. But, that assumes the headlight is 7" mounted with fork ears rather than a "halo" and it depends on the master switch. Also, if planning on electronic ignition and/or a solid state rectified/regulator then all the harnesses have lots of extra wires to contend with.
I know it sounds daunting - it's not really and if you think in sections, it's easy.
Ignition (make spark)
Charging
General lighting including the taillight
Brake light wiring
Turn signals
Horn
Basically, they are separate. For instance, with points, and 12volt coils it only takes one wire from the battery minus connected to the minus side of each coil, a ground wire from the battery positive to the engine casing, and the Black/White wires and Black/Yellow wires connected to the coil plus terminals to run. Then to keep the points from pitting, a condenser to ground on each side. If you have 6volt coils then you need a ballast resistor between the battery and coils. Obviously in any case, a fuse and on/off switch are a good idea!
You mentioned that the headlight was an "S" type that should mean that your serial number is below 135088 and that the headlight is mounted with a "halo".