About the only part of a V-8 HEI you can use in a V-6 will be the basic housing casting, the module, and maybe the vacuum advance. You'll need to alter the length of the shaft and/or the position of the drive gear, fit a 6-lobe reluctor and pickup coil, and probably do some alteration to the centrifugal advance curve. The distributor cap and rotor are different, too. If you're using the coil-in-cap dizzy, the coil should interchange from 6 to 8 cylinder engines. I do that alteration occasionally, but I've got a machine shop and a distributor tester handy, plus 35 years' experience with the HEI systems under my belt.
Jerry
