I need to run my electric choke to a 12v source that is powered by the key. Will my tach slot running to my hei distributor work?

 

no. run it off an ignition run fuse like the radio. the tach is a signal and isn't a constant 12v.

 

Also wrong. Do not run the choke off of the same circuit as the radio, or any other shared circuit for that matter.

Electric choke produces heat, so it needs a good, isolated 12v power supply. Run a fused wire directly from an ignition switched source on the fuse panel.