What were the differences in dash speakers?

Some of you are aware that I make and sell a bracket for mounting twin 3-1/2" speakers under the dash to replace the old style single-cone. This isn't a sales pitch here (see "CAR PARTS FOR SALE" for that). What I am finding to be the case is that there apparently were different sizes of speakers used over the years in our A-body cars. I wish Chrysler would have kept it simple and used the same size over the years, but that would have been too easy.

I want to build templates for the full range of applications for all models of Chrysler cars and trucks, where the old single paper cone speakers were utilized. I need help from all you guys willing to provide me with tight measurements taken from your respective vehicles' speaker mounting screws.

Depending upon how tight you want to keep the tolerance, for the 4"x10" speaker in my son's '74 Dart Sport, it measured 11-7/16" between (center-to-center) the two mounting screws under the dash. For simplicity, let's call it 11-1/2". If you can get within 1/16", it will be good enough. It will be interesting to see how big a variety of measurements I will receive. For some of you with a car dismantled for repair, it should not be much trouble. For others who are willing to crawl up under the steering wheel, A/C-heater, and dash, it will be a bit more challenging, and I appreciate it.

I've already gotten a few measurements, and it seems that the earlier models used smaller speakers, but even then, I'm getting a variety of lengths. It would certainly simplify everything if someone could definitively prove that all cars between "this year and that" used "this size" and all others used "this size."

Long story short... I will appreciate any insight you can provide for whatever vehicle you can, whether it's an A-body or not. I hope to do the same for all the other Chrysler car and truck series, as well.

Thanks in advance,
Jerry