74 dart has electrical power but no start

splice the two yellow wires where it goes into the interlock reset box?

Yup. Look at the link I posted. There's a horrid picture of what it looks like. On a /6 Gold Duster I just junked out, it was on the left fender apron.

Has a red plastic reset button.

Picture of the connector and box at the bottom of this thread:

http://www.forabodiesonly.com/mopar/showthread.php?t=14304&highlight=interlock