I believe you are referring to the stud bolt at the exh port on the cyl head.
If installing header on NA1 engine and unless the header is using extremely thick flange for some reason, then I recommend replacing all stud bolts to the NA2 spec, 90026-PV0-000.
It's shorter and has better chance of surviving against corrosion/rust over years as the threaded section is protected by the nut.
If you look at your existing 91-94 spec stud bolt, you will understand it especially if they are all rusted.
The longer exposed thread section would be very rusty and some cases, you would take out the stud while loosening the nut (not a problem).
Even the 95+ NA1 spec stud (-P0G-) is bit shorter than the 91-94 one but again, unless the header flange is massively thick, go for the NA2 -PV0- one.
At the same time, for the same reason, I recommend replacing all the nuts to NA2 spec 90217-657-000.
Unlike the split design of NA1 nut, this one has better treatment and will survive longer against corrosion.
Ideally, you should replace the metal gasket between the header and the cyl head and if doing so, again, please select the NA2 spec 18115-PBY-J02.
The exh port size and the geometry on the cyl head as well as on your header are not accurate and not consistent.
You won't be able to see it but quite often, the geometry of the header port opening doesn't necessarily line up properly against the exh port on the cyl head.
It's a tiny difference but NA2 gasket has slightly larger hole size than the NA1 one so you may gain just a tiny bit of non-disturbed extra flow.
In the above photo, overlayed NA2 gasket over the NA1 one and you can see the tiny difference in the hole size.
Good luck.
Kaz