Thank you Pista
Thank you very much for the help. I dont have too much experience with rebuilding engines. Only learning to do it now. So I have no experience with copper gaskets. Will make sure everything is as clean as possible and see if i can put some other sealer around the water and oil holes.
Do you think its necessary to skim the block aswell? The surface still looks decent, but it is an old engine and you can see some marks here and there.
Considering if the engine is still in the car, I'd not worry about getting the block deck skimmed as it would mean removing everything and disassembling the whole engine - in that case you'd probably want to be changing out pistons (ideally to lower compression to suit the turbo system) and reconditioning everything while you're at it..... I would, however, clean the deck meticulously as discussed. What I would definitely do is check cylinder head gasket surface for flatness....referring to the trusty Nissan L16 & 18 Engine (1973) Factory Service Manual (thank you Nissan Motor Company.....), the procedure set out in the picture below (on the left hand side of the page). It involves using a straight edge (a steel rule should be OK for this) and feeler gauges to ensure no part of the gasket surface of the head has a clearance from the straight edge of more than that in the table..... If you're not sure, or if there is some indication of warpage of the cylinder head surface, I'd be getting it double checked at a reputable engine reconditioning workshop - if there is an issue, you'll be going there anyway!
While you're there, you could get the cylinder head hardness checked, like 'd' suggested in the post above, however each engine shop may have an opinion on what specification to use for a Nissan engine (I'm not sure....) and the FSM doesn't call out a specification. Typically, however, if the engine has NEVER been run overheated, you'll find the head material hardness will be fine....