Not sure I can answer all your questions...speaking from butt:
An ignitor, if I'm not mistaken, is basically a solid-state replacement for the points/condenser, and would typically fit inside the distributor (at least the ones I've seen do).
I pretty sure an 87 did not come with an HEI distributor--that would have been a mod. Ignitor, if present, would have replaced points/condenser. So no part of the HEI replaced the ignitor--other way around.
I'd be reluctant to put the 60 ignitor in an 80 (assuming you can)...