Block VIN # help.

That looks like block serial number on top pic, in 68 Vin stamping started roughly half way through the year and I believe only HP engines were stamped. And 68's were stamped behind driver side head on trans bellhousing rail if it were stamped. Your serial number reads:

PM=engine assembly plant Mound Road
318= displacement
R=regular fuel
2265 using mopar 10,000 day calendar is Tuesday, October 10, 1967
0419=engine sequence assembly number