I'm using GMCBubba's Mopar/GM Hei ignition for my 52 chrysler hemi and I had a difficult time finding a good working GM HEI module. I went thru two new ones from Pep Boys and two new ones from NAPA. I even tried the Echlin which was bad before I left the store. After getting the first bad one, I had the store check each one before I would buy it. As a result , four new ones were checked and were all bad. I finally found one at Auto Zone, but I don't have much faith in the cheaper units. I'd like to carry a spare in the glove compartment. Any suggestions will be appreciated. Thanks.