Ok, got it working, will post up how I figured it out incase anyone else in future needs to know and finds this.
Yes you do definitely need the manual speedo cable, if people tell you the auto one will work THEY ARE WRONG. The cables are different.
After thinking how I could try each setting trial and error on the speedo gear drive without putting it all back together and driving it, i realised i could do the following instead.
Jack the front of the car up so you can get the speedo cable unscrewed, take the speedo gear drive bracket off, drain gearbox oil, take the speedo gear drive out, spin the plastic gear at the back of it and make sure it spins the key/slot in the front where the cable mates into it. If it's all working, then,
Jack the back of the car up now so both wheels are off the ground, release handbrake, put in neutral. Put the speedo gear drive in at any setting you want to start with, no need to bolt bracket on, just put the gear drive firmly in, then simply spin the driveshaft by hand and watch to see if the end of the speedo gear drive spins (where the speedo cable mates into it), if it doesn't spin, just spin the speedo gear drive around to the next setting, spin the driveshaft, watch to see if speedo gear drive spins or not, and keep going through all 4 settings until you find the one that works.
Once you've found the one that makes it spin, put it all back together, fill 'er up with gearbox oil, and away you go.
Worked fine for me, now it's just trying to figure how far "out" the speedo is due to the auto diff
So if anyone knows how far out it is or if there is a way to correct it, let me know pls!
