I have a 1952 M38 Jeep with a late 70's Buick V6.  I replaced a lot of wiring and the ignition switch so the problem is likely my fault.  The engine starts up and runs great, but when I shut off the key - it keeps running.  If I pull the harness off the alternator the engine stops.  Or, if I pull the wire from the ignition switch (I think) to the distributor it also stops.  When I reconnect the harness to the alternator or the wire to the distributor it starts up normally again.  Someone suggested I put a diode in the exciter wire to the alternator.  

Stumped.

Gerry  

sounds like the ignition switch isn't shutting off the power to the dist.  

It sounds to me like your alternator is still sending power to your distributor after you turn the ignition switch off. If you have an internally regulated alternator  the excite wire needs to go to a separate pole on your ignition switch than your distributor power feed wire.  I did this with my 3A...it was an adventure.  

are you using points or a hei?  

John Cappa,

You were bang on.  The distributor wire and the exciter wire were on the same circuit through the fuse box.  I routed the exciter wire to an unused pole on the ignition switch that was hot when the key was turned on.  The engine turns off now which is darn handy.  Thanks for the tip.

Gerry  

Well, I am not John Cappa, but I have met him a few times (and he photographed my jeep in my Avatar). Glad I could help. I did the same thing on my 3A and had to put my hand over the carb to get the engine to shut off...It was fun.