1967 340

Curiously the M is for Mound road. 340's were built there from 71-73.(My 72' 340 has a M340 on it.) to be 68-71 it would have a W.The space after 340 usually says R or P for fuel type. I did see a 340 once in a brand new 75' Cordoba with a two Barrel.(back then I rented it, and the air cleaner said "340") So, it could be one of the last as well. Which side is the timing mark on? my book also said that some blocks had the seven digit series cas a part number, not 10,000 calendar. However, The Part number for the 68' short block does not match that number.