Thanks everyone,

Got it sorted. The terminal for the feed wire for the circuits was bad. I went to pull the terminal off on the hot side of the fuse block and the terminal came apart. It was a female spade terminal with the wire coming in at 90 degrees. I was able to trim enough wire back to use a standard female spade connector to replace the bad one.

Regardless, I think it is time to go through the electrical system and give it a thorough inspection/renew. I have already rebuilt the harness to the rear and to the engine. Really need to redo the engine one as the car has a MSD 6AL so there are a bunch of redundant wires I can eliminate. I have to believe the under-dash harness can be greatly simplified as I run no accessories on this car. Going up on wire gauge is not a bad thing either.

Anyway, the problem seems to have been high resistance in the supply wire for those circuits to the fuse box due to corrosion/deterioration in the removable female spade terminal.

Best regards, Dave