Casting dates

the build date numbers wouldn't be on "either side", only before. in other words, the block couldn't have been produced and then installed in the car AFTER the car was already built....generally, the build dates on 68's should be between a few days up to 60 days before the production date of the actual car.

 

I would expect to see dates on your car 2-4 weeks prior to build date. There was a strike in the fall of 67 that delayed a lot of 68 early production. On my Jan car almost all of the dates fall in that range with the exception being some of the outside vendor items (carb, smog can)
Tim

 

With 68's/69's, there was less fiddling with the engine. So, anywhere from the build date to 2-3 months before is acceptable.
With 65's/67's it's harder to peg. For instance: Acording to Pony Carbs, my 715 carb was built in March of 66, and they suggested it was a wrong date. I figure, well, that was on the car when I bought it in 1971, looked original then, so I figure Shelby might have bought these carbs by the pallet. Also, I have C3 and C4 numbered hi-po exhaust manifolds, not the C7 numbered ones, those too were on the car when I bought it.

 

For 68 Holley made the carbs in lots. Every C8ZX A (GT 500) I've ever seen had a 7A4 date (4th week, Nov 67). I believe KR carbs have a similar common date.
Tim