1990 mustang crank no start

Did you have spark before you replaced the dist and ig module? If so, check to make sure new parts are wired correctly (double check it). then swap ignition module to see if it works.... if not, then it would seem to be your distributor.

let us know how you make out...

Fwed

With the vehicle cranking, is there a tach signal anywhere?

I believe the blue wire, from the ignition module, carries the rpm signal to the computer. If there is no signal, the vehicle won't start.

Test that circuit for a dc pulse, if you haven't already. Any codes?