What ignition system are you using? Mallory Unilite? How old is the module? Mallory revised the module a few years ago which makes it more reliable. Also, has the car been welded on before these symptoms started? My 6AL box was exhibiting the same symptoms when the box got hot (mounted on firewall above starter solenoid - car would die, pull over, sit for 5 minutes and it would start back up, then repeat after another couple miles.
I just installed the Pantera Electronics EIS - very well engineered, great features, and fantastic support from Jon! Costs slightly more than an MSD or Mallory box, but American made and many more features than either of the mainstream Chinese-made boxes offer! So, well worth the investment!
http://www.pantera-electronics.com/eis.htm
FWIW, I'll be adding the Pantera Electronics EIS to my Mustang as well.
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