This may not be as easy as it first appears! There are several varieties of dipstick available from Continental, and only one is correct for an O-200A in a Cessna 150. None of them fit
both C-90's and O-200A's (according to Continental). There is a 5qt and 6qt dipstick!
http://www.tcmlink.com/pdf2/SIL00-7A.pdf 
