I have an F/54 block mated to a fresh rebuilt N-42 cyl head barely shaved less than .5 of One thousands. This is the first valve job done on this head. It has new valves, seats, seals and professionally cut 3/angle valve grind a well done head.The block is a flat top rebuilt in early 2004 i believe bore over 1mm. It has a chromed valve cover with engraved 3100cc stroker. Yes a rear piece.Cylinder head was just replace on block and clad with new injectors and seals. It's still in my 1975 280Z but car is still on non op so it;s sitting in my garage. If you are interested in this setup and want pics, i can only get them to you by text to a cell.