I have a 1967 SS, no A/C. I purchased a RetroSound M2 stereo for Christmas. I have newer Pioneer speakers installed by someone else in the back that look good and speaker wire is already run to the front. I just pulled the old (original I think) center speaker from under the dash. It has totally dissentigrated, the only thing left is the magnet and the bracket. I am wondering how I am going to mount the new speaker I ordered from Summit Racing (RetroSound D-412). The old/original mounting bracket does not look like it will fit the new speaker (speaker is on the way so I can't dry fit it yet). Any ideas, tips, or tricks to install the speaker is greatly appreciated.

 

It should be a 'Plug & Play' replacement. The new mounting holes are in the right place for a 4X10 OE speaker.
Good luck.

 

I was able to make the old speaker mount work by using to piece of flat iron and the screw hole in the back of the speaker.
My next question is about wiring the ACC 12V wire. Right now, my tach is wired into the ACC 12V connect on the fuse block. can I splice both the wires for the Tach and the Radio into the one ACC 12V connection?

 

Yes you can