Speaking of the trunk divider - does it go on the cabin side, or the trunk side? I bought the speaker set on ebay and I can't quite figure out how the 1/2" board the speakers are mounted on goes it the car. It doesn't seem to want to fit either way. Since the '57 didn't come with the panel, I don't have a template to check the speaker board against. I assume it is supposed to be a jam fit as I don't see any mounting holes or brackets. If anyone has installed one of these boards or one like it, I would like to know how it was done. Thanks!

When Injustice Becomes Law, Resistance Becomes Duty

The 55 panel is mounted on the trunk side. It uses a combination of sheet metal screws and metal tabs, which are an integral part of the body. 55-56 dimensions should be the same, but I don't know if the larger 57 trunk is different. The panel has an upward curve on each end of the bottom of the panel. The top of the panel has rounded corners, but otherwise pretty straight.

I'm looking at the aftermarket panel/w pre-mounted speakers in Larry's 1955-57 Thunderbird catalog. The description states that it is "designed & engineered for 1955-57 Thunderbird to fit with no alterations to your car." The shape of their panel, however, is not exactly the same as the OEM 55 panel. It does curve upwards on the bottom ends/w a notch just above the curve. The top, however, is not rounded on the ends, but has larger notches, probably to allow for the trunk-lid hinges to clear. The bottom curves should be for inner wheel-well clearance. You may have to drill holes for sheet metal attachment screws, along the edges/perimeter of the board. 

If this does not suffice, I suggest you contact the vendor for further instructions.