Here was what I wrote about the ’69 and ’70 Mustang on Autocade. Corrections welcome: most of this is from memory with the odd fact (like production numbers) checked in books or specialist sites. The pic, obviously, is of a ’69, as one can tell from the grille. PS.: I have added what I wrote about the ’67s and ’68s at the bottom of this post so we can see the evolution from the original models.
Ford Mustang. 1969–70 (prod. 494,334). 2-door coupé, 2-door fastback, 2-door convertible. F/R, 200, 250 in³ (6 cyl. OHV), 302, 351, 390, 428, 429 in³ (V8 OHV). Enlarged Mustang as muscle-car battle heats up. Semon ‘Bunkie’ Knudsen, new Ford president, ordered that Mustang had to be the ‘killer street machine’, losing its compact origins. Wheelbase unchanged but car longer and wider. Fastback called Sportsroof. Ford attempted to lure buyers from the personal–luxury market of the Pontiac Firebird with the Grande, with Cobra Jet 428 at top of range vying for muscle-car market. Mach I and Boss models became collectible additions. Styling cleaned up for 1970, though sales fell considerably, to 191,363—performance bent, which seemed right for ’69, seemed to suit the new decade less.
Ford Mustang. 1967–8 (prod. 789,525). 2-door coupé, 2-door fastback, 2-door convertible. F/R, 200 in³ (6 cyl. OHV), 289, 302, 390, 427, 428 in³ (V8 OHV). Mustang’s first revamp saw improvements in most areas, slightly muscular styling, and more cubic inches as horsepower war began. Wheelbase identical but car wider by 2·7 in. Shelby GT-350 returned, but Carroll Shelby also introduced GT-500 with 428 in³ with claimed 355 hp—though it probably had more. Emissions’ regulations began to affect ’68s, even Shelbys, though cars themselves had detail improvements. Bullitt fastback among the ’68s; 428 Cobra Jet introduced for this model year. Shelby GT-500KR (King of the Road) took muscled-up Cobra Jet engine: Consumer Guide suspected close to 400 hp rather than claimed 335. Sales fell more for ’68, however, probably due to increased competition from GM and AMC.

