The HEI distributor is much larger in diameter than the conventional distributor, about twice the size. This is to prevent the spark from jumping from one spark plug terminal to another. The HEI trigger module is mounted to the distributor base, and has 4 wires, two from the outside, and two others connected to the "pickup coil" which surrounds the distributor shaft. A "coil-in-cap" distributor will have a 3-wire plug which connects from the distributor housing to the top of the cap. The 12 volt power lead is also plugged into the cap terminals. The remote-coil distributor has a somewhat different wiring harness.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!