It is NOT a Satellite, the 2nd character "M" stands for Medium trim level, Satellite is "H" for high trim level! Without my books in front of me I can't say for sure, but it could be a Belvedere! Also, I believe that "F" in 1968 = 273!!
I still say check the casting date on the motor, and the stampings on the trans to verify which year they are from! Another thing to check, although it could've been changed, is the casting number on the center section of the rear end, which should be either a 741 or 742 if correct! A 489 case would not have been introduced until 69!