Help! We have a 1969 351W date code 8J3 with a M cast on the back of the block on the passenger side. We can't find any info as to what this means. Can anyone shed some light?

 

I'm not sure what the M means. The best resource for this would likely be Bob Mannel's book Mustang & Ford Small Block V8

It's a wonderful book full of detailed identification charts and illustrations.

I borrowed one years ago, but at the website's price, I might as well pick one up for reference.

Good luck.

 

Are you sure it's "M"? How about "W"? ...for "Windsor" foundry....

 

It's an "M" Out of 13 C9OE blocks there is only one with the M cast into the back.
date code 8J6 and not 8J3

 

Found out engine served duty in a 69 Shelby GT350.. Thanks