Compare your engine to the pic on this page
http://fomoco.com/index.asp?Dept=Resources&Tool=Textbook&Eng=7
6: 1966
S: Pilot Plant
68 is the body serial code for 2 door Fastback.
L is ?
103472 is the consecutive build number which began at 100001 so this car is the 3,472 car built.
63c: 2 Door Fastback
M: exterior paint color White
25: interior trim Red Vinyl
15b: date code 15th of Febuary
84: is the district code for Home Office Reserve
9: 4.11:1 rear axle
5: 4 speed manual
Sounds like this is a rare car.
Ed Jenkins
Galaxie Club member #3350
1966 Galaxie 500 Convertible built in Chicago Illinois, still has factory orginal 352 FE with factory C6AF-L 1.12 Autolite 4100, and many more factory parts. Car is in good condition.
Please visit the Carb Forum at
http://network54.com/forum/88781