Converting to HEI, need 12v (Ign 12) source

"Thanks for the confirmation. I had tried connecting the brown and blue but was not getting 12v on crank. I am not getting voltage from the brown coil+ wire on crank, so I have a problem to track down somewhere."

This gave great information, and you do indeed need to find out why this is like Del suggested for the loss of power in the crank position of your ignition.
Otherwise a switch will be required. (you could even think of it as a theft deterrent if you hide the switch) :-)

Personally, I'd prefer mine working like it should.