It will not work on the 69/70 without repinning the connector into the printed circuit, as the layout of the pins within the connector differs between the tach and non-tach underdash harness. Just passing this one along for those 69-70 owners who might think what works for 67/68 would work for them.
I agree - it's a piece of cake to get the engine to run- as said previously just conect the male and female tach leads, that makes the series circuit with the ignition complete and away you go. As far as the idiot lights-back-to-gauges, the oil sender needs to be switched (cheap fix) and the ammeter circuit connected. Not really difficult to do. Easier to go from tach to non-tach than the other way around - also you can make a LOT of money by flipping the tach unit if you wish to go to the oil/amp gauge layout.