[FC] eng number

[RON BLOOM]

Good morning 

I have a question regarding a eng.. I have a 65 open . went to do some work on the eng and found that it reads out, the last 3 XXZ. What does this stand for? Also there was a freeze plug in the right rear corner of the block. Looks like to me this motor  could be used in my greenbrier and I would have a 110 .. Any history and comments would be appreciated.... 

Warmest Regards
Ron
Tucson, Az
62 greenbrier
65 open