I've built the complete "American '66" long time ago...
they were (as Richard says) from Hasegawa, perhaps i can make pictures from the boxes. Nice to look at, the T-Bird is the...hm...worst of them.
If i remember, they have three different underbody (same base Caddi/ Pontiac , same base Chevy/Buick and shortest the Ford). Also the dashboards are the same, only different decals.
Cadillac:
Pontiac:
Chevrolet:
Buick:
Ford: