Long time to get back to this, but finally done with some floor pan repair, painting, wiring...etc, etc, etc....and ready to install these seats.
Thanks for the tip on the Mazda seats Gydyup. I had already leaped before I looked and acquired some white leather seats from an '01 convertible.
Just wanted to update my findings on installing these seats in a '66. I'm guessing the OEM tracks on a '66 vs a '67 must be slightly different because I had to use a little different spacers between the tracks and the seat frames.
This mainly had to do with the secondary track or the track that is not controlled by the release lever (this is the RH track if you were sitting in the seat on both seats in a '66...it's activated by a turnbuckle type link connected to the primary track which is activated by the release lever).
On this secondary track the release mechanism needs some additional clearance between it and the seat frame or upholstery on these 99-04 seats. Long story shorter, I had to add a 1/4 inch spacer between the seat frame and the secondary track on the passenger side seat, and use full 1" spacers all the way around on the driver's seat to allow clearance for full actuation of the release mechanisms on the secondary tracks. I used the 1" spacers all the way around on the driver's seat to keep it uniform. I only used two 1/4" spacers on the passenger side seat secondary track, because I only had two on hand and was pressed for time. Looking forward to bolting them in this afternoon.