All Small Six Part numbers and date codes

This relates to all small sixes
Would a 65 Mustang with a scheduled build date of 29 K (October 29,1964) have a part number on the block of C4 or C5? Mine has C5DE-6015. I can’t read the stamping above the draft tube, is that where the date code should be?

Head has a number cast in the back of the intake are of the casting that’s 3F18, which is June 18 1963? If I’m decoding the right number in the correct way means the heads been changed with one from 63?
 
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Curious if anyone has any help with the above question, or could point me to a source that might have the answer?
 
I can only provide my opinion but Ford used all parts they had on hand till they were gone so it seems possible they had a 1963 head to use. I would go to one of the Mustang forums where restoration is a focus for probably very accurate information.
 
Thank you for responding.

I have asked at two different Mustang forums, but no replies yet. I thought this would be a relatively simple question to answer, especially the block casting number.
 
There are casting codes and part codes. Your 65 stang could have parts with c5 a as a well as c4 although since there aren’t many 64 1/4 mustangs I would think most of your parts would be c5. Especially if it is not a real early 65 production date. If I remember right, casting numbers don’t reveal the decade. Only the part numbers, eg. C5 would reveal 1965
 
Also very likely the original block/head were changed before you owned it.
 
Can you please clarify the build date. Is it from a Marty report? A casting code of: 29K could be either 1965 or 1966. You need to find the number with C5___ or C6___. That tells you the actual year.
Hope that makes sense
 
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