Marcos Maniacs

Hey Guys,
                Well I got a call from my mechanic/rules committe contact for 
vintage racing. The rules commitee dosnt know  a lot about the Marcos and I 
am having trouble getting a engine ruling. Now in 1966 (chasis 5006} my car 
came with a 1500cc moter. I have brochure stating that a 1600 was also avail. is 
this true? While I was on the Unoficial Marcos home page  it looked as though 
in '65 ther was an 1800 avail. am I reading this correct? If so are the 
engines interchagable between the two years? I was hopping to be able to race this 
year but having an uncommon car is difficult for the common race official. Any 
help is greatly apreciated.
Hal
#5006