I was hoping someone could help me.  I had to change my U-Joints and was able to clean off my differential.  Can anyone tell me what this number means:

2 FA 2 12 68 W

It is stamped on the bottom of the differential, not the cover.  Thanks,

The "FA" = 3.70 ratio, heavy duty posi, for a 427 car
The "W" = Warren Motive, the plant where it was assembled.
The other #s indicate the date of build(Julian date)

Thanks Adams' Apple.  This is another indicator that my car was a 427 car from the factory.  Maybe you can answer another question.  If I was to put a 427 back in the car, even though I cannot document it, would it still be considered a numbers matching car?

Thanks,

Simple answer: No.  The engine would have to be the exact one that came out of the car, which means the VIN on the engine block stamp pad must match the VIN of your car.  It's very rare, but there have been cases of present owners contacting past owners, asking lots of questions and then locating the original motor in someone's garage.  However, those are usually cases where the original motor was less desirable and a more desirable motor was inserted.  I can't imagine why anyone would replace a 427 unless the block was badly damaged, althought people do things you wouldn't expect all the time.

With that said, if you are into originality, you can install a 427 cast within 6 months of the build date of your car and have a "correct" engine for your car, according to the NCRS guys, although it still does not carry the higher value of the original motor.  Also, on a 40 year old car, there are probably far more components than just the engine that have been replaced with "service replacement" parts that make them no longer original - things like brake calipers, alternators, starters, water pumps, etc.  If the majority is not truly original, I'm not so sure having a non-original but correct motor in your car woud add much value.  Of course, the smile you'd have when you hit the gas would be priceless ;-)  

I suggest that before seriously considering that kind of investment, and 427 blocks, heads, etc., are very expensive, that you get on the technical discussion board at ncrs.org and start asking questions.  Or better yet, start by searching their archives, as this exact question comes up all the time.  Not only can they give you EVERY possible clue to check to verify the original configuration of a '68 as a 427 or not, they can tell you exactly the date codes needed on all parts to be considered a "correct" car (not #s matching) and the likely investment vs. increase in the car's value.  

BTW, love the Vette!  Even though I have an '81, if I ever add a 2nd one, it would be a 68 or 69.

Thanks chesh, I am really into driving the car, the numbers matching thing for show car status is not really my game.  I want to modernize the suspension and steering, then a new 5 speed, so that it runs/rides more or less like a new (2000 era) car.  You just can't replace the way these cars look with a new vette.

Jr,

Did you find the diff #'s on the flange( lookin underneath, where the cover meets the main case)?  If that's where it is, mine is so faint I could barely make them out. I've tried Brakeleen, WD -40, you name it, to remove gunk. Maybe I'll try smearing white paint on it then wiping clean.....hopefully the numbers will appear.

JR

That is where I located the number.  There is a space there between the spring mount and the strut rods.  I sprayed PB Blaster and rub vigorusly with my fingers.  Good luck.

Chesh:
          Believe it or not when the gas lines grew to almost a mile long and you could only get gas on alternate days in 1973 IT WAS NOT AT ALL UNUSUAL to swap out a Big Block and drop in a more gas friendly small block ...

I know at least a dozen guys who did exactly that... Remember this 68 was all of 5 years old  at the time  ands most likely was a daily driver

... I was driving my  Corvette back and forth to work  at that time
and ordered another Vette (.... OK A CHEVETTE  !!!)  in oder to afford to drive to work...It was a Scooter...cheapest model they made..& even deleted the radio...  

My point is really that it was pretty damn common to either sell a BIG BLOCK Car at the time or swap the engine out for anything that would let you avoid the gas lines ..

I live in what was a very rural area then
(early 70's) and I and almost all my neighbors had 300 Gallon Gas tanks at the house...However The Farm Supply company that supplier our gasoline cut off residential gas delivery just so they could supply the farmers with their needs... another reason to pull the Big Blocks
out and drop in a small block...

There are plenty of 65 thru 74 EX BIG BLOCK Corvettes  on the street today... and many of them that are on the street with BB's under the hood do not have the original engine ...

Bob

Thanks.....I'll try PB Blaster and a brass brush next before the white paint.

JR

Great point Bob.  I was 7 in '73 and remember the gas lines, my dad complaining about gas prices, and my brother selling an Olds 442 and buying a Vega, but I guess I was also young enough that it didn't have a direct impact on my at the time, nor an emotional one, so it isn't something I immediately think about.  Now, had I been a proud owner of a 427 Vette and had to make the tough decision to replace it with a mouse motor, you bet I would remember.  That had to be like sacrificing your first-born...  It had to be bad enough to be a car enthusiast old enough to see the muscle-car era collapse into a period where you could not buy a factory performance car.