The 1967 Auto World catalog mentions the MPC Miller "91", as well as the MPC "Stilleto", a show car commissioned by Bob Larivee and built by Ron Gerstner. The same catalog also mentions an AMT Porsche 911 in 1/25 scale.
The 1969 Auto World catalog lists a Jo-Han 1969 Roadrunner convertible kit, but it never appeared. Years ago, I was dealing with a collector in the Midwest, who was selling kits for someone else. The guy who had the kits (a two-car garage full, stacked from floor to rafters) gave the seller an inventory list. On that list was a Jo-Han '69 RR convertible kit. Both guys tore the garage apart looking for it (the seller was a Mopar fanatic and wanted that kit) but no such kit was in there.
AMT announced several 1970 annual kits that never appeared, including an El Camino, Mercury Cougar (MPC made both hardtop and convertible, but AMT stopped after '69), Falcon, Corvair (in this case, Chevrolet stopped after '69), Cadillac Eldorado (likely a re-boxed Jo-Han kit), and Galaxie XL fastback. Other 1970 AMT kits that did appear differed from the announced versions (LTD four-door and Buick Wildcat were originally $2.00 customizing kits but appeared as $1.00 unassembled promos, the Chevelle was an SS396 instead of the 454 that was issued).
AMT announced a 1977 Gremlin annual kit. The 1:1 '77 Gremlin had new front end sheetmetal, and the V8 option was dropped during '76 (fewer than 500 '76 V8 Gremlins were sold) so AMT would have had to make a lot of changes to keep the kit correct...so they quit after '76.