According to some private correspondence I had with Walt Anderson former President of MBCA and a 5-speed owner:

In 1986 there were 781 US legal 5 speeds imported to the US. There were none in 1987 and 311 in 1988. There have been none since 1988. These figures were quoted by MBNA in a letter to C. Robert Beltz, MBCA Legal Council and Past National President.