I'll be running what JTS calls stage 1, which is L16 on standard seats. I'll be using standard rocker gear (may upgrade later)and a nismo headgasket.
I'm steering clear of fly cuts in blocks etc

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DuraPro then modify the fire rings with a special jig I made specifically for the job. It supports the bore of the fire rings but allows some stretching of the valve relief whilst still holding the fire rings flat. The fire ring Dia and cut out for the valves has to be changed to suit the big valves with high lift cams. Its a bit fiddly to get right but once its done it works well. This arrangement has been good for over 12 months now. I tried Nismo head gaskets but the relief for the valve is not big enough and it had to be stretched too much and I was concerned the base material for the gasket was bruised and wouldnt seal.
Re tensioning is required once it has settled down after heating and I usually pull the gasket down an extra 5 Ft pounds.

so what head gasket do you use then??

I appreciate the replies guys.

In the past we've use Camira Valves for the purpose, 7mm stem, Pulsar Valve guide?

The only reason we used them was, they were there and had a smaller stem.

Yes Rhys, with big valves you have to have some relief in the block..something Im not quite confident in doing myself at this stage. Jeff Taylor is the man ...

Its all possible. I run 41mm inlet and 33 exhaust with cut outs in the block. Only issue has been finding the right head gasket to seal between the centre bores because the cut outs a fairly large so wall thickness can be an issue. But it is doable.

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Thats an extremely valid point. I heard of some bloke who took a beutifuly restored triumph vitess to some IHC mechanics,(actually a whole bunch of them doing a "mechanics" course) to have a lumpy cam fitted. The valves excceded the relief in the cylinder walls. Bent valves, and broken rocker arms were the result.
Come to think of it, Dattodevil did some work on that car too.

Do you think you would get away with cutting the reliefs on an assembled shortbock? Probably not aye.

Jeff Taylor built my head with 40mm inlet and 33mm exhaust. The problem you will have is with the larger exhaust valve, if you have a cam with large lift or if you have shaved your head for better comp or both the exhaust valve will hit the block. you can cut a notch in the block but i had to cut down 3-4mm which can get a bit close to the top ring.

You probably could but rocker angularity and the resulting side loads on the valve stem would have to be carefully looked at.

Normally we use a shorter stiffer spring (holden) to get over the coil bind problem.