Would 68 cuda bucket seat tracks fit a 71 dart?

If the 75 has a catilytic converter, no.

I dont know why the 68 tracks wouldnt work. I thought they were interchangeable from 67 up to the appearance of the catilytic converter (1974?) that put the hump in the DS floor that changed the DS inner track.

Like I said in my previous post, I'm using 69 tracks in a 72 with no problems.