It begins again - 512 Stroker

Ordered my 440-512-5075 kit today. Need to make decision on heads. Early 70's 3462346 casting (right in pic) will need new guides installed or Late 78' 4006452 casting (left in pic) will need hardened exhaust seats installed. Both have 81.5cc chambers & will be ported using DC P4120437 plastic template kit. Not sure of the benefit of additional water circulating holes around spark plugs on 78' heads (see pic) but they do match the block. Any experience is appreciated.