I had made it as far as identifying it to be either a 35, 40 or 41. And while I know there is a conversion kit to eliminate the points I think that puts it over the top as far as money spent to make the ole girl sing again. Incedentally the prop is an 18 x 6-10 Pro Zinger non-constant pitch prop. So that is really no help as it covers the entire range of props you mentioned.