I did a bunch of these conversions , it's easy, only requires a grinder or a file.Just hack off the retaining ring on the aluminum distributer body, don't touch the area below the retainer, fits just fine in the 235-261 or GMC distributer hole.Then compare the old and new dist shaft just below the drive gear,it needs to be shortened about 3/8 inch and then reprofiled to match the original tip. I made a new hold down from some scrap steel,saves butchering the stock hold down. On some engines, the large HEI cap may foul the oil dip stick tube, you can bend the tube, but the stock stick is not flexible enough to fit back in.So then you need to use a thinner stick from a later Chevy and remark the full and add lines.These modified units work just fine, no problems, I have run them for 5 years.The Petronix unit works fine too I'm told,if you have to buy a HEI distributer and new plug wires,a module, it winds up costing the same as the Petronix
HEI modification
