My thoughts would be as to why the exhaust side studs are rusty whereas the inlet side are not.
Appreciate that you will replace the studs but where did the water come from ?
Hence my comment that they sit just inside the water jacket . If you remove the plugs in the block on the exhaust side you can see the base of the studs. This is why I asked the question about sealing the thread to stop water creeping up the stud.
I was recommended ( and used) permatex 56521.
https://www.permatex.com/products/threa ... ant-50-ml/
I’m in no way an expert on this and others may well advise otherwise
Tim
Series 1 FHC purchased 50 years ago. Courted my wife in it.
Series 1 2+2 when the kids were small now sold.
Series 1.5 OTS in opalescent maroon, Californian car. My retirement present.