The casting #'s are the raised #'s cast into the block. Try these two links. The info you seek should be there.

http://clubs.hemmings.com/clubsites/chevytalk/GMhistory/index2.html

http://www.mortec.com/location.htm


"If it ain't Steel it ain't Real"
"Earth the insane aslyum for the rest of the Universe"
41 1/2-ton, a work in progress
68 Shortbed stepside 327/325hp/700R4