Be sure to check the voltage on the positive side of the ignition coil and feel how hot it is. Also check the resistance of the primary coil. What type of dizzy are you running? Generally speaking you will want to see 0.7 Ohms resistance and 9.0 volts while running on the positive side of the coil. If you see anything higher than that, your ballast resistor may be shot or may have wiring issues.
I had this issue on my boat for years and looked right past it assuming that since it ran cold it must be a carb issue.
1985 Supra Comp TS6M
351 Windsor - 240 HP
Velvet Drive - 1:1
Fully Rebuilt