A fusable link.
If it's an automatic, most likely a Turbo 350.
The wiring diagram for a 1969 Chevy C10 truck is located in the service manual. It outlines where each electrical component is located and how they are wired together.
I think it is 18436572 usually stamped on intake manifold on the old Buicks.
Not sure, but you might find an old Chiltons manual on Amazon or Ebay.
i have the the full wiring diagram for the entire truck i can e mail you
garry G&L AUTO REPAIR
The firewalls should be close enough to work they may be some differences from vehicle to vehicle though
NO. The latch system didn't come into play until somewhere around mid 2000's
Most auto glass companies can probably get that for you, but if they can't you might need to start contacting wrecking yards.
Probably around 16 mpg. I had a 1969 LeSabre once and the best I got out of it was 18.6 on the freeway.
Check your local library ,they usually have repair manuals.