This is a Davis Unified Ignition distributor by Performance distributors this thing rocks though i had to modify the distributor hold down with a plasma torch (enlarge it) because the shaft on the new dist. was larger in diameter, and remove the engine pull bracket with a die grinder so the distributor would clear. all it needed was a switch 12v and a tachometer signal all from the old coil wich was no longer needed because it is all built into the cap of the HEI. whats cool though is when you need a cap or rotor just go down to the auto parts store and buy a GM part. Other then that it was very easy install.