73 Mustang wont start...

I've tested the r-lb off of the ignition switch in start and it shows hot. However when testing at the starter motor relay the r-lb wire is not hot (thus not turning over). However I can hotwire it across and it runs. So it is mostlikely a short in that circuit. The wire diagram shows a "start interlock back up lamp switch" I presume connected to the trans somehow to prevent starting in gear? Could it be shorted? Where do I look? Thanks for the help.

Thanks..

The info is much appreciatted. I tried the start in neutral, still a no go. I have alot of play in the shifter, so I'm going to dive under and replace the A331 bushings anyhow. I'll check the switch and see if it's just totally out. Thats about the only place I can think of between the switch and the starting motor relay, unless a short in the line somewhere. Thanks again!

Neutral Safety

I can hotwire it from the battery to the S terminal on the starter relay. The S terminal would be the hot lead from the ignition, by way of the neutral safety switch(if it worked. So in hotwire to the S terminal I initiate the relay, not bypassing it all together. Sorry for the confusion.

I found the neutral safety switch, farther forward on the trans, on the shift linkage. Pulled it off and it rattles (it's not supposed to do that is it? ;-)) I have no idea what happened to it all of a sudden to just pop the rolling terminals out of location, but it did. They are pretty worn, so I'm gonna go ahead and replace it. Hey so why does the 70-73 C4 neutral safety switch cost 2-3 times more than the other years? Just my luck.