Still can't find the right rails to mount my 75 Dart bucket into my 73 Duster, but I did find a set of '69 Dart rails...are they the same? I know that 70-74 are the same, but I suspect that the '69s are different. Anybody tried this?

Anybody?

Like you, I would expect they are different, however, knowing how old Mopars are often similar, I'd bet you can get it to fit without serious problems. The holes in the floor should be the same, but because of changing safety requirements over the years, the seat attachments are probably different.

I did pretty much what you are trying to do. A '70 Dart (which has the same floor), and '&5 Duster seats, with a set of '67 Baracuda tracks. I had to drill new holes, and use creative spacers to level things out. The seat bolt patterns are all the same. The floor patterns differ from year to year, so you REALLY need to have tracks for your year car if you want it to fit with out modifying things. I didn't mind cobbling things up a bit.