Date will be on the pass (other) side.
From what i've learned the -dash- # indicates the # of castings or revisions that particular mold has made.
-1 would be the first -2 the second so on.
Thanks 66V100...will check out the passenger side again. Very hard to see the block with the header in place. Need to dig out the old "mirror on a stick" to get up in there.
And thank you everyone else for the explaination of the "1".