With my shortened cylinder barrel stock pushrods are too short and H's pushrods too long. I shortened H's pushrods with a lathe by the correct amount to have the rocker blocks staying in the middle of the acceptable tolerance before tightening.
Between 1mm and 2.5mm according to H's documentation so I targeted 1.75mm.
H's documentation in a better English than mine
Reassemble with the new pushrods following the reverse of the above sequence. It is important with the pushrod
positioned on top of the lifter with no cam lift, the rocker and rocker housings are then placed on the head with the
fixing screws loosely attached with no pressure. At this stage it would be expected for there to be between 1mm
and 2.5mm gap between the base of the rocker housing and cylinder head. (If the valves are being held open
beyond this, there is too much preload which can be solved with a slightly shorter pushrod). When you then
tighten the 4 fixings this gap will close up. Due to the oil in the lifter, it is very likely that when tightening the rocker
housing the valve will open. You must allow 10 or 15 minutes for the lifter to “bleed” before turning over the
engine. This should then allow the valves to close.