[Brett James-McCall]

Fred,
If you look at the timing chain area on the block it should have two bosses protruding frontwards either side. The number is a block from the Mustang line and is alleged to have a higher nickel content than an ordinary block. The deck height should be 8.206

D=1970 decade
1=one, so block is 1971.
Z=Mustang Carline
M=Mexico or Performance
This is a good block.
Old Mexican blocks bored 060 have been know to make 250-300 dollars on ebay!

BTW I also have one.

Brett