The car is finally on the road. Got helped across the line (by a very-generous-with-his-time) Jed from Buzzme to help untangle the mess of two looms grafted into one. What looked like 45 mins work was actually a full 6 hours with Jed troubleshooting half a dozen other small odd problems that also came up, while I spent the bulk of the 6 hours swapping a return fuel line from the donor car to my car - a surprisingly tough job.
Other odd problem, when I connect the (yellow with green trace from memory?) taco wire to negative on the coil, I can see the taco twitch when I crank the car, but the car absolutely won't fire, only crank. When I disconnect the taco wire from negative, the car starts up fine, but the taco remains dead. I tried connecting the taco wire to neg on the second coil, and got a massive backfire when I turned the key, so immediately stopped playing with it after that. Any hints?
Final issue, the brakes have gone spongy - no idea how the engine swap affected the brakes. Unfortunately, the maiden voyage I didn't crank the handbrake on hard enough, and when I returned to the car after helping the girlfriend move into her new house I found the car had rolled nose first into a ditch, smashing up the driver's quarter panel some. D'oh! Time for more panel beating and another touch up.
yeah the yellow with a green trace is the taco wire, it goes from the - negative on coil 1 ( if connected to + 12v side may cause issues) to the taco in the dash, the dash is powered via the Green with a yellow trace . you said you had electrical issues ?? when you looked at the wiring and pieced together 2 looms??
ok this can cause some major issue when using 2 looms from different years. you original car was a S1 929 wagon "right". the doner car was a 75-77 929 wagon??
with the emission upgrade in the later model it changes 10% of the loom and pin outs are different and i had some issue when i used a late model loom in my 74, i had dead shorts and battery issue due to these differences and had to repair the original loom to fix the issue ( since then i have just repair/rebuilt the hole loom)..
with the brakes going spongy maybe you have installed the 1 way valve to the booster the wrong way and will give a soft pedal feel but brake will still work
hope this helps