TBH sounds like the cometic gaskets, didn't know they made a metal plenum gasket, was interested what Rod runs on his ?

He said roughly £80 for a headgasket which I assume is group A

Personally I would not run a group A on stage 3 with 100 shot of nitrous as I'd expect problems

I think the spec is lo comp, head studs and the £80 headgasket which he claims will take 500bhp, I've already told him that is a load of crap, bottom end may withstand it but headgasket certainly wouldn't.

No idea who has specced this, I know he is having it all specced and machined then his old chap is building it

Its up to them which route they go down but in my opinion I can see a lot of money being poured in and problems coming from a badly specced engine, some of the spec sounds ok but sounds on its limit if its only group A gaskets,