I'd use two HGs myself.
Its not like you can use instant gasket or glue on it.
Besides, once torqued down the HGs should compress and provide a seal anyway.
Of course I could be totally wrong here but I just dont see the 'sealing to head' idea working.

Sod knows on the bolts. Try the usual suspects. Burtons and the like..
What are you doing? Turbo'ing a standard block?

If so, why? Cant be hard to find a turbo block instead. Or are we talking zetec?