It doesn't matter when it is first registered, if it doesn't have a Co2 emissions figure on the v.5 it can't be taxed at the 2001 rates.

The first registered doesn't apply to new imports from the U.S eg. 2008 Mustang is only £185, so I can't see it applying to the M.5 unless it has a CO2 figure.

From DVLA;
The rates shown only apply to cars that have been type approved in category M1 and registered on the basis of CO2 emissions measured in grams per kilometre (g/km) driven. These details are shown on the Registration Certificate.

Type the reg no. in here, it will tell you if it holds details;
http://www.taxdisc.direct.gov.uk/Evl...vent=link.next
.