The cheapest option would be to just fit a YBO611 head gasket with standard bolts. It isn't really up to the job of 380bhp, but it will last a few thousand miles of hard use and maybe nearly 6-7k of mild "occasional" abuse.
However, fitting a METAL headgasket requires both surfaces to be planed flat and there is NO POINT in fitting one, if you aren't going to do this
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You could then get someone like Ahmed to map the EPROM to suit your spec, which will need some ignition / fuelling and boost changes (due to your car still being 8:1). This will give you around 350-360bhp (the limit of the standard compression with a T34). But at least you will have your ALS and a bit of extra fuelling in hand with the greys. If you speak to him nicely, he could even sort out lamda control for good fuel economy as well
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