No spark..what should I check?

I have my engine ready to run, but I have no spark. It is a 5.0 into a 66 coupe. I suspect that the TFI module may be bad, but every test I know to run on it says it is fine. I had intermittent spark, then I only had one spark, now no spark. Of the six wires on the TFI connector, one is blue/red and goes to 'starting/charging system.' Where exactly should this wire go? I've been working on this for months, but now I don't know what to check. I appreciate any help I can get.

Thanks in advance,

Gary in GA