How to remove this #$%$#* bolt

OK...I guess you just have to be forceful....I put the socket on an extension and gave it a whack with a rubber mallet....and bam...right in.
Now the bolts are out, but I can't get the head loose. I tried prying, whacking with a block of wood and no dice...what next??? Also, do those casting numbers mean anything that I should know???