i almost forgot, the radio ground is "poorly to the dash"
it's silly to realize all the troubles the designers went through to reduce noise and interference with this delicate radio design
and then just let it have a random ground path through paint and rust
i recommend adding an explicit ground wire from inside the radio on the main chassis on the power transformer side, bring that out and screw it down on the fire wall
this will ensure the antenna ground plane (aka the cab) is reasonably well connected to the radio guts
you want to minimize any current flow on the antenna coax outer shell, connecting the guts to the firewall will help a lot with this goal
if you were to float the radio electrically while it's turned on, it would operate, and 100% of the ground current would flow down the antenna coax shield to where the antenna mounts on the cab
if your antenna coax shield is not tied to the cab at the antenna base you won't get as good a signal and your radio will be susceptible to RF noise
make sure that antenna shield ohms out low to ground before plugging it into the radio
-s
