This is where I found my year for my motor. The 3350852 is a 1972 and the 4075351 is a 1974.
The first serial number for the year of 1972 would be 3235063 and the first year of a 1973 would be 3478003. Your first serial number is between them two so that makes it a 1972. The 1974 year started with the serial number 3816308 and the 1975 serial number starts at 4141450 so your second number is between the 1974 and 1975 serial numbers. Your first number, sn 3350852 a 1972.That makes your second motor, sn 4075351, a 1974.
In the interim, here is a link to the condensed version of the Clymer manual to help you get started. Download it soonest to your computer as the link is short lived. The manual applies to both s/ns.
