cvh manifold studs
 

Wanted to replace my inlet & exhaust manifold studs, can anyone confirm that these are just m8 by 50mm or are they some sort of imperial size?

Defiantly M8. I got exhaust studs from Burtons.

Ya I've just bought some from there as well. I like how they have a torx bit at the top to make getting them in/out easier. Is it worth trying to get the old studs out that are stuck or just leave them even if they're rusted?

If they are just rusty and untidy, I'd soak em in wd40 and wire brush them. Then run a die over the thread to freshen them up. If they are in need of replacing, just soak them in wd40 for a day before trying to undo them.