About The 1980 Mustang
The public was excited about the new 1980 Ford Mustang and all went well in 1979 so Ford was feeling a little better, too. In 1980 the changes were minimal to the exterior yet the performance this year was pretty bad. The engine just was not up to par and did not perform well at all. In addition to this the usual price increase from year to year was more from 1979 to 1980 than normal. However, there were 271,322 Mustangs sold in 1980.
Source: Mustang Forums