help with casting numbers please

i decided to finally check the numbers on my 70 dusters motor wat i came out iwth was
block-"25360303186" now im guessing it means it is a 76 318 does any one have any info on this motor and suggestion with what to do with it to get max hp out of it
heads- i took off the valve covers and one cast said "360" then near that was an "L" and a casting number ofn "3769971"
i could really use the help because i am trying to decide which direction to go with this or another motor thanks in advance