that bolt isn't accessible from the inside, it's a boss that doesn't penetrate the firewall - use a pry bar to lever it out as you turn it w/ the wrench - once out tap it a size larger and in future make sure you keep it tight, likely corroded from being loose or maybe stripped overtightening - there's a similar
one lower down that carries a ground to a starter mount bolt - good factory setup to insure proper ground to gauges and misc interior electrical
and welcome to the garage, from the smokey big Island
looks like you got a winner from the start
Bill
