Check out Joel's post in this thread:
5.0L (1979-1995) Mustang - 5.0 won't start/run with spout installed - I've been troubleshooting a continuing shut-off and no start condition for some time now (thank God I have a second vehicle). I started by replacing the distributor because everything I read was pointing at the pickup or TFI...
mustangforums.com
Wasn't sure if you had done this or not.
Additional checks I found from one of his older posts on the Corral:
1. For the wiring check, measure continuity from pin 36 at the ECM connector, ECM and TFI module disconnected, to the SPOUT pin at TFI connector, if it reads @/over 5 ohms, need to trace the wire for an open.
2. TFI and ECM disconnected, key on, check pin 36 for voltage to ground (short to VPWR if you read any voltage)...you can use pin 40 or 60 as your ground reference.
3. ECM and TFI disconnected, check resistance from pin 36 to pins 16, 20, 40, 46 & 60 (short to ground if you get anything below 10k ohms).
4. Same as 3., check resistance from pin 36 to 26 (short to VREF if you get anything below 10k ohms).
5. Same as 3., check resistance from pin 36 to 56 (short to PIP if you get anything below 10k ohms).
Everything checks out?....replace the TFI module....problem repeats after the TFI replacement?....the ECM would be next.
Not sure what happened to him or where he went but I cannot find any new post from him on the Corral or the Yellow Bullet and he used to post regularly on both. Guy was (hopefully still is) a trouble shooting guru.
Did you ever verify that the balancer is good to go i.e. outer ring has not slipped on the inner?