Ok I may get deleted but here goes , THE DUI , is NOT a great setup , it was designed for the mid 70-s-early 80s to help fire the Very lean mixtures that they were running , in order to do so the had to increase spark gap , to do so they needed a higher power coil ,and that also meant an increase the distance between posts on the cap and bigger diameter plug wires to contain the extra energy and resistance created by the Plug Gaps , Now your saying , sounds like a high performance setup , BUT , when you package a Module a Coil and the Magnetic pickup ( along with metal advance weights ) all in close proximity of each other , they better get along well or it wont be good , AND , THIS SYSTEM was to work on Engines That never saw the High Side of 4900 ( including Corvettes of the time !!!!, I have been a Mechanic since the Mid 70's and I had a job at a Mobile/Modular Home Plant ( They Had there own Garage ) part of my job was maintenance on 17, C65 Chev Trucks , that ALL had HEI's in them after about 30,000 miles the coils would die , or the modules , then the Wires would arc , or the spark would punch through the rotor and leave the truck stranded ,Fast forward to now , 35+ years of Experience ( plus I recurve/rebuild Dist's for a living ) I can tell you now that the Davis DUI's are No different then the mid 70's design , its just they fit the 6's ,( barley , there Big and Ugly and look WRONG on any Ford ( IMO) The aftermarket came to the rescue with the HEI , they removed the Coil from inside ( accel still sells the kit as does MSD ), then the made a kit to use a MSD or other Brand of Module/Box that is NOT inside , GM themselves later realized that module failure was due to heat soak ( inside a Dist is not Cool after a few miles ) , so they made it mount external ( GREAT IDEA ) , Although Ford , and Best of all , CHRYSLER , had always done that , If you Want an Upgrade , Use a Duraspark I , Or II , add a MSD Box, or equiv , ( the DUI Duraspark /Chryler's Module is good as well , but again pricey ) some here have bought the DUI's and like them , this is not a Dig on CI , I just want to clear up a misconception that The DUI is a Outstanding Piece, Ive said this before , Nascar Dosen't use Them , and there is a reason .