I think the 'extra' hole you refer to would be the one at the bottom for water drainage ... the correct mounting screws should cut in enough to get a good ground ... if your body doesn't supply a good ground you probably don't have the battery ground wire connected to the right place, which would be to the boss just behind the battery on the firewall - then there's also a ground strap from the toeboard below to a starter mount bolt

Bill


Moved over to the Passing Lane

"When we tug a single thing in nature we find it attached to the rest of the world" John Muir
"When we tug a single thing on an old truck, we find it falls off" me
Some TF series details & TF heater pics & Rust-a-holics Unanimous parking lot