Can anyone point me to a good explanation of how to do a HEI conversion for my 1975 454?  

Install the distributor and hook your coil+ wire on the side of the dist. cap where it says BATT. The other vacant terminal is for a tachometer. Its that easy.  

OK I forgot to add that it has an internal coil. So it needs a non-reduced feed. I guess typically it's about a 7 volt feed but this needs the full 12 volt.

I've searched the internet for instructions but they are usually vague or non-specific.  

Trace the wire and find the resistor. Remove it and you will have your 12V. If cant find it, run a new wire from your fuse block that has ign. power.  

OK I have done as you have instructed but I'm getting no spark. I have tested the power end with a voltage meter too. Anyone have any troubleshooting ideas?  

Did the HEI work before you hooked it up? The only thing I have had any trouble with is the module and the pick-up coil. Take off the distributor cap and rotor, then pull the dist. Drive the roll pin out of the gear and pull out the shaft. The module is a rectangular box in the front of the dist. It has a plug-in on either end of it. This is the likely cause of your no-fire condition. It is a cheap part that can be had at any auto store. The pick-up coil is a small, round winding, centrally located in the dist. housing. Its failure results from the two small wires attached to it, breaking over the course of time. This piece rolls back and forth everytime the ignition advances and retards, and sooner or later the wires will break. If your getting 12volts to your batt. lead, the other plug is snapped in place, and your cap is assembled properly, then I would change that module. By the way, whats that 454 in. Probably has 781 heads. Can be a sweet motor.  

OK I've narrowed the source of the problem: The 12 volt source I've found turns off when the engine is in the 'crank' position. I can't seem to find one that stays at 12 volts in both the on position and the crank position.  

What about the original coil wire?