We did pull each fuse one by one and had continuity through it all...my buddy thinks the voltmeter and/or light bulb might be causing the continuity...we did close the doors so the door switch to the dome light wouldn't be a factor.
Ran new wire through the firewall plug, rewired alternator over to starter relay with #10 wire and fusible link, cleaned up firewall connections and DC-4'd them, cleaned up fuse box, and some wiring left over from a failed attempt at electronic ignition years ago (think I had a lemon control box). Once wired up there was no continuity to ground on either side of the fusible link going to the firewall...so I guess the idea of the voltmeter or light bulb providing continuity didn't pan out in this case. Pulled 5 amps through the firewall with the ignition switch on. Mr Duster started right up and the voltage is good. Voltmeter rock steady now too which is nice. My buddy did find the dome light inop so we'll trace that down another day. Happy to be able to drive it again! Guess I was bit by the dreaded corroded power plug terminals through the firewall. Next time I see the voltmeter not rock steady I'll investigate instead of waiting till I have a problem. Thanks for the advice Dubob! Happy Moparing....