Very timely question as I have a new speaker for my 55.2
Measuring this morning the new basic monoral replacement protrudes into the header panel by 7/8 in. and requires a 2 1/4 inch hole to clear the new magnet. The original used two holes and trim out the triangles left between. The original speaker had one side of the coil grounded to the body with a screw hiding under the speaker cover. The other wire was the feed from the radio and it was a single wire fed in through the header hole, down the inside of the "A" post and over to the radio laying just above the glovebox cardboard. The radio has a single terminal plug. (think of a RCA jack without the ground shield) I hope that helps Joe, I have a copy of the original GM 4 page installation instructions that I could fax to you if that would help. It came with my new replacement speaker,(from the Filling Station) so you might get one as well from your supply house.
Howie. Ham call sign VE6GT
