69 z28 engine decoding help

I'm trying to see if my engine is the correct engine for my car. the block has a casting number 3970010. the casting date is M47 which does't add up. the vin is stamped by the oil filter housing where it should be and looks very professional done.  the block has been dected to where there is no numbers on the front pad.  I was about to give up when i found some information on M date codes. www.camaros.org   theres a paragraph  on M coded blocks.  the way i read it there is no way to determine the date on M coded blocks.  Just woundering if anyone has run into this before?  Im going to try the acid etching to see if i can bring some numbers back.  Doe's anyone have any input  on this?     Thanks mike

True, the M can't be a date code since the date codes are A-L (January-December). Even though the write up says you shouldn't have a date code, out of curiousity did you look to see if there was a date code at the bellhousing on the passenger side of the block?

I would say that, if you have a 3970010 block AND you have the correct VIN stamped by the oil filter, then that should be proof enough that you have the original engine to that car. (As long as the VIN looks authentic). Consider yourself lucky that you may have one of the few smallblocks that actually have a VIN by the oil filter. As you know, most were on the front pad and were often removed by decking.
Here are some more sites to check out...
 
http://www.chevy-camaro.com/chevy-camaro-engine-codes.asp
 
http://www.68rscamaro.com/69cams/
 
http://www.blake.com/oemcarbs/chevy1.htm
 

Yes the block casting date reads M47. which the 0010 block wastn't casted untill the year of 69.  But this block looks like a older block by the different structure on the sides of the lifter valley. also the front pad where they stamp the block is big like the older blocks were.  I know the later 70's they change the size of the front pad. so you think if this block was a 1977 block it wouldn't have any of these features.