[davedew]

I assume in number 2 you mean a black wire from the bellhousing bolt directly to the negative of the battery.

Also are you still using the Sierra fusebox, as I don't recall there being any earth wires directly out of the fusebox.

Out of interest have you tried shorting from the main battery feed on the starter motor to the small impulse connector on the starter to see if it turns over?

Been re-reading some of your posts. Is the battery new / fully charged / in good condition? Your initial test with a multimeter could show 12v because it is using hardly any current. As soon as you apply a load to the battery if it is dead it could show 0v.

Shorting the starter as above would show if the battery is good or bad.