.........And there's an old but good thread by AbodyJoe on this with photos
How To Install an Ignition Switch in 1970 Dodge Dart
It is ALSO possible that the switch IS NOT BAD which is why you need to do some checks first. There are several areas of concern and we here can step you through this
1.....Even though this is a 73, it might have the 74 seat belt interlock which I mentioned earlier
2.....There could easily be a wiring problem, a bad connection in the bulkhead / firewall connector, or at the ignition switch connector
3.....Depending on how the push button is wired, there could be a problem with the neutral safety switch wiring, with the switch, or simply the transmission linkage not properly adjusted
4.....And of course it can actually be a bad ignition switch
