The Opel Manta A was sold from 1970 to 1975. The base engine was a 1.2 liter making 60 horsepower, while the top engine was a 1.9 liter making 105 horsepower. These cars were sold in Europe and the United States. They were even sold in the United Kingdom under the Opel name, which is unusual because most Opels were rebranded as Vauxhalls for the UK market.
The Opel Manta B was sold from 1975 to 1981. The 1975 model would be the final Opel sold in the American market. The B1 models had a much more aerodynamic look than the Series A cars. They were very similar in appearance to the Chevrolet Monza.
There were several special edition Mantas sold. One very rare model was the Turbomanta. With a special S spec engine, these cars could make 156 horsepower in a very small and light body, putting out performance numbers that could crush most supercars of its day, including the Porsche 911.
The TE2800 was not an official model, but it was a special project by a private company named Transeurop Engineering. They ran into a lot of problems when Opel refused to work on the project with them and help out with several engineering problems. Only 79 of them were ever made.
These Opel Mantas are rather scarce in the American market. They are sold through some private companies that specialize in Opel parts and repairs, and you can find them listed on eBay, which is where I would go for Opel Manta parts and used cars.