One reason that power seats were not available on the Cordoba 300s was due to the lh cat converter and related hump in the floorpan. The manual seat tracks were about 4" apart, so they used 1/4"-3/8" aluminum plate adapters between the seat tracks and the seat cushion mounts. So the existing seat cushion for single exhaust cars could be used. Perhaps you might do similar, but between the floorpan and the seat track bottoms, to shift the seat rearward an inch of so? Or use some of the same material to put under the front mounts, with longer bolts, to tilt the seat rearward, possibly?
In 1966, they had manual seat tracks which had adjustability in them. The individual seat tracks were two-piece items, with bolts holding things together, with adjustment slots in them for customization of the seating position for the driver. A forward or rearward tilt, plus possibly a bit of extra movement rearward, too? Might be a salvage yard part? Page 23-61 in the 1966 Chrysler Service Manual. Adjustment ranges and illustrations. That was the last model year those tracks were used, fwiw.
Just some thoughts,
CBODY67