Re: 65 convertible front seat
Posted this in another thread, but when it comes to bucket seats, the 1964-66 seats are interchangeable between Galaxies and T-birds. However, the seat bases - i.e. the rails that attach the seat to the floor - are not. Galaxies seat bases have a longer footprint than T-birds. But the seats themselves unbolt from the seat bases and can interchange. From there, only difference is the fabric pattern.
The 1965-66 split/non bench seats will work between all full-size models. Split bench seats were made for 2-doors. 1967 seats will also fit. Given the wheelbase is the same between 1965-68 Galaxies, I'm willing to bet that 1968 seats can bolt in as well. Surely someone on this board can confirm.
Main considerations about interchanging seats are twofold - one is the seat width. Obviously it can't be wider than your current floorpan and door panels. Second is as mentioned - the seat base. Different bases are meant to attach to different floorpans. However, they can be modified with flat metal or U-shape bars and high-grade bolts. Never weld here, they can fail with too much G-force under hard braking.