I agree with the above and will add this to hopefully clarify what he is saying,
You have an Ign 1 and Ign 2 circuit. Ign 1 bypasses the ballast and applies full battery voltage to the coil for a hotter spark when starting. Ign 2 goes though the ballast resistor to limit the current through the coil and prevent overheating the coil.

This is a short summary not inteneded to cover the why fores of why it is what it is.
In short ( no pun intended) if it starts in the CRANK position and dies when releasing the key to the "run" position you are not getting voltage to the coil.
Look for a disconnected ballast, (Easily done when re sealing an intake), or a bad ballast. Could be a bulkhead problem, ignition switch problem etc. The most likely candidate is the ballast or connections to it.
To Confirm, Jumper battery Voltage to the coil, hit the key, if it starts and runs your halfway home. UHH do not run it this way for an extended period. you May have to pull the Jumper to shut the motor off. Report back