What we call the "z-type" here in Europe was sold in 1978 and 1979. It is known in the US simply as the '79-type.
There was an A-type in 1980 that was also sold in the US. It was black, had reversed Comstars with a black inside and a "glove compartment" in the rear behind the seat..It also had Air assisted frontfork, 5 row oilcooler and a bigger dynamo. I think it also had "apehanger" bars. More importantly, this had improved rollerbearings in the rear swingarm, better carbs, and more "open" pipes that sounded better.
Here in Europe the Z-type had a bit more horsepower than the A-type, because off californian emission laws or some other #$%*. About 6 hp I think.
Like Nick said the Egli framed version is very cool, but it's not the only framebuilder who tried improving it. Here are some other good ones:
Moto Martin (France)
Bakker (Netherlands)
Spondon (UK)
Schurgers (Netherlands)
Motoplast (Italy)
Egli started out with the famous Vincent Black Shadow, tuning and modifying it for local mountainraces in Switzerland. He build his first frame to improve on the Vincent, the bike was unbeatable and that started his career as a framebuilder.
Egli frames had a thick 10 cm toptube, that was kind off a trademark for him along with the colour red he painted his frames. In 1981 he made a frame for the cbx, and together with Target design for the bodywork they tried to sell an improved version of the cbx. It wasn't very succesfull.
A year later came the "red baron" on of Egli's favorite bikes. This was also available as an overbored 1200cc version. It was fast and steered good, but wasn't much lighter as a normal cbx. The frame was not all that different from original either.
The price off a new "Red Baron" was double that of a normal cbx, so you can imagine that then didn't sell that many. Today they are almost impossible to find and very expensive.
Here's a pic off a nice Egli:
There's some nice video's here too (they take ages to download):
http://www.xs4all.nl/~fritshe/euro-movies/