Identify this engine

[rhb1999]

I'm new to this forum, so bear with me. I have a question regarding the casting number and engine code on a Pontiac V8 I have. The number on the top rear of the block is "10000708", there is also the number "78" to the right I believe of this number. I noted an engine code on the front passenger side near the top of the deck stamped "X-9". The Wallace Racing webpage says the code indicates the block as a 1978 Pontiac 400. Another website I looked at says it's 301, but this and all other information about the 301, do not have the code "X-9". Also, did this engine come with a 2bbl or a 4bbl. The heads are stamped "01". Thanks in advance.