The IC timer is a LM555, sourced mine from Radio Shack. Do a search on LM555 you find many schematics, the values of a resister and a capacitor determine the timing. I experimented on my bench to come up with about 5mins after ignition “on”. The timer controls a simple Bosch type relay to handle the heater current. Power comes from the ignition “run” circuit at the ballast resister. The original application for the heated choke spring I used was a 74’ big block thermoquad like this one.

The original choke control looks like this. Again, should you go this route it will likely fail pretty quickly. I did take the power resister off and used it on my home built timer control.

Pictures borrowed from currently running ebay auctions BTW.

I will post more pics and a diagram of what I did next week, I have much work to do on my car this weekend as it is off to the body shop next week for final paint.