I was about to take it on the weekly little trip around the neighborhood. (needs front end rebuilt, etc. not serious road worthy but a few miles here and there fine)

I was all started and warmed up (edelbrock 4bbl on intake, no choke hooked up), which takes a few minutes even in summer.

I put it into reverse and it died.

Electrically.
Not it was not warmed up and going out of parked stalled it.

Like you have when you lose the ground.

Neg terminal to block ground is good and tested.

No power at any fuses.

I am scratching my head about why the lose when go out of park.

My seat belt safety is looped off, and connections are good.

Last week, the fasten seat belt message light was on, which I do not remember seeing before. But not on the drive after that.

I am thinking my first step then might be I should pull the seats and carpet and see if it is a short in the seat belt wiring.

Any better ideas on where to start if good ground off batt and it happened shifting.

Thank you for any tips.

Seat belt only keeps it from starting it won't make it stall.
If you have no power at all it may be the bulk head connector ammeter connection.

Thank you.
I stopped on the way home from work and picked up a 14 and a 16 gauge fusible link in case I needed them.

Jump to red to yellow on the relay did fire up the starter.

fusible link showed good on multimeter.

red from fusible link to bulkhead male spade showed good on multimeter.

The bulkhead looked great.

I cleaned both male and female up, put it back together, and I had power again.

Not sure why shifting from park to reverse was the exact moment it went out.

Not sure why only one time I have seen the fasten belts message light a drive or two before this,

but it is running right now.

My harness is on borrowed time. Old, dry, stiff, and splices everywhere.

If it is the fusible link the headlights will not work. If it is the ignition switch the headlights will work but anything that gets power from the switch will not.

If it happens again check for headlights. I had a similar problem and it was the switch going in and out.

My 73 use to pull the same thing, try checking the wiring loom under dash for \broken / cut wires Then proceed to steering col plug in and look at the connection almost in center there should be a 10-12 gauge wire mine was melted and green, I jumped past it and she starts right up, next Fuse box you may just want to get a parts store box and eliminate the stock one with the glass fuses the fuse connections are generally the problem they aluminum corrode and the fun begins. I only do that as a last resort when I have had enough of being under dash