The Langdons unit is vacuume advanced, and the Petronix is installed in your existing dist. by removing the points and the plate that they are secured to, don't know about the Mallory. All three will need a new high voltage coil.
I chose to go with the Langdons unit because if you blow a module in Lone Jack MO. you can get it at the local auto parts store. All the outhers you are there for a couple of days until you can find a module and have it shipped in.
The only thing you need to get for the mimi HEI is a set of wires and a coil. The coil that Langdon sells is for a Ford 300 six. You can pick this up on your own if you feel it nessary.
Just my 3c
Tom
