To determine if it's pre 64 you need to look at the serial #. The approximate last serial # for 1963 is 2586000 according to my copy of the Blue Book of Gun Values, any serial lower than that is Pre 64.
In response to the original question I would say the Marlin 336 is a great gun, it doesn't have anywhere near the nostalgia factor of a Winchester 94 but prices for used Marlins are steadily increasing. The only Winchester 94s I would consider would be pre 64 versions. The only Marlin 336s I would consider would be JM marked guns built before the Remington buy out. Rumor has it Remington is putting out better guns now but I still wouldn't chance it until that's been proven.