That's good descriptive history, where was that taken from?
You have no date casting on the bellhousing flange that looks like what's in the link below (2nd pic)? Sometimes the casting is on the passenger side, top of bellhousing flange.
Camaro Decoding help on Chevy-Camaro.com

 

Engine Stamping Numbers

 

i had someone look at it last week and told me it was made september of 1968 and was out of a 1969. this guy wants the block because its a 69 but is saying he put that dz stamp on there years ago.....so i think he's trying to get the block for cheap. he just picked a 69 z28 to restore and is buying another z28 in a couple weeks, also a project. i just dont think i can trust his word on it.

 

I wouldn't trust him either, he's looking out for himself to "steal" it from you.
Like I said, if it's a forgery, it's a darn good one. The style of the numbers look correct, and they all line up and look like they're the same depth.
If someone hand stamped those numbers, you should be able to see some inconsistencies, if even a slight bit.

 

well the z is alittle out of line just by a very little, but other stampings i have seen(not dz) the last letter is off alittle also. so im just alittle.... yeah..

 

well i guess im puttin this thing up for sale as a dz then.