If you lost a timing chain it would make a different "sound" when starting. It would be more of a fast whirrr instead of the usual "heavy grunt." If the timing chain is busted only the crank/pistons are spinning. I've popped a couple on Toyota 22R engines and they make a much different sound when turning over, in addition to the sick feeling that you've just destroyed the pistons/valves. Luckily on old chevy motors, they're not zero tolerance and you can just put a new chain on
Is your motor a straight 6 or v-8?
Sounds like an electrical issue. My vote is wiring and/or control module. Check your fuses too!!!! Are you using a 12V wire to the HEI or did you use the original wire that went to the points coil? That wire only has 8V going to it.