A little back-story...I am building a '79 saloon using mainly pieces from a donor '75. The '75 is setup with discs and beefier aftermarket arms, etc. There is no floor in the '75 as it was rusted and cut out.

This is more a question out of curiosity because I am looking at both outside of the car and still scratching my head...a solid mount sub out of a '75 (2 - 5/16" retainers on each tower) and non-solid mount sub out of a '79 (single large bolt on each tower).

Aside from the difference of the tower mounting, I measure a difference in the horns to be about 3" (of course, I am aware of the mounting difference of the horns). For grins, I threw the twin-tower mount subframe into the '79 shell thinking that the extra 3" of horn would make contact with the shell. It doesn't.

I do plan on using the subframe out of the '79 (single large bolt on each tower) for my build but still wanting to know what else about it makes it not line up without extensive fabrication?

Is there a difference in the design of the floor of each shell (remember, I do not have a floor in the '75 for comparison), is there something in the tower location?

Does someone know? Like I said, this is question out of curiosity. Thanks!