my 289 engine casting code is...C5AE- 6015B......with 7L15 below it
this means it's a 1965 block ( C5 )..but the code date is 1967 november 15 ( 7L15 )
can this be true? a 65 block cast in 67?

 

Yes, this can be true. The "C5AE" is merely an "engineering number", meaning that the part was designed in 65. It was used for several years though and the part remained the same.

 

the date code tells you from when this block is. so November 67. So your cars date code should be around that as well. if you have a 67 from july then there's something wrong.

the 6015 means engine block, nothing else. the B means it's already the 2nd revision of this 65-model block. don't get the C5 as date code. take it as when did they first make this block. little changes to it are only reflected in the revision. so all normal once your car is end 67 as well