R-5651 was the number assigned to prototype/engineering car #EX-2944, according to the build sheet, Before the records were given to the museum, SASCO used to have a picture of the (build sheet) one for EX-2944! The serial# it was given was R-5651, (one higher than my other source indicated). It was a supercharged, 4 speed; grey with red and elk interior. The final assembly date is shown as 04/03/62; but the date of that form, is 04/03/64! Is the "04/03" coincidence, typo, or fabrication? The "TAS" on the form was "change serial# and destination". It went to stock, in lot 151. This is one of a few '63 engineering prototypes. I've read that some were updated to '64 specs and sold long after the assembly line closed. I wonder what became of it. It appears to be one of the '63 engineering cars that was updated to '64 specs and sold long after the 'last Avanti". It has option "75 3.73 axle ratio (Power Lock Axle)". Has anyone seen "Power Lock", before. The standard '64 rear was 3.54, with the 4 speed; although it had been 3.73, earlier.