Also, what exactly is the difference between a GT and a GT-X? And what year did they start getting the L20A engine? Wikipedia (yeah...) makes it sound like the 2000GT-X was coupe(KCG10), and got a 120hp L20 starting in 1971, while the 2000GT was a sedan (CG10) and got a 106hp L20A "the following year".
But I found a site that lists detailed specs for cars sold each year, and it lists both sedan and hardtop 2000GT's with L20A engines @ 118hp, starting in 1968. For 1971, you could get H/T or sedan 2000GT's with either 118 or 123hp L20's, or a GT-X H/T or sedan with a 128hp L20A. So is that what makes a GT-X different, that it's more powerful and can be had with a 5-speed? Although oddly enough, the 4-speed is listed as having better acceleration, since all the gears up to 4th (1.00:1) are lower.
GT-X is basically the luxury-spec, so it had a twin carb engine (similar setup to the zeds with twin Hitachis) and blingier trim and grille etc. Interior colours were plain black in the GT but the GT-X would get say brown seats with dark green carpet. Also the GT-X had power windows and a/c.
AFAIK, the L20 6cyl was available in the C10 sedan pretty much from the get go in 1968 as a 105hp 4spd in the 2000GT. This was bumped to 120hp in 1969 (still with 4spd) and then in early 1970 you could get a 3spd auto. Then in late 1970, the coupe was released, with the same 120hp/4spd or auto and it wasn't until late 1971 that the 2000GT-X was offered, with the twin carb motor and that extra 10hp. Still 4spd tho, and then in 1972 you got the 5spd as an option on both 2000GT and 2000GT-X.
No Kev, you are eating a duck fetus.