To buy or build a new engine?

Hi,
I am now going to build an AC Cobra replica based on an AK 427 kit here in the UK. I would ideally like to use a Chevy small block and like the power to be around the 400 bhp mark. I used to build engines so would be happy to source the parts myself and build one myself, the problem with this is knowing what components to fit to achieve this power and also is it really cost effective to do it this way? I have been looking around a few websites and it seems the companies in the states do well priced turn key engines but then I would have to pay shipping, taxes etc or if not try and source one from a uk engine builder. What would you guys suggest is the best way forward? Any advice or links to websites will be appreciated so thanks in advance.
Roy.

Sorry can't answer your question Roy but I hope you are going to put a 5 speed gearbox behind that motor and not another slush box auto???

Yep I'm with Evolvo on that one a chebby in a Cobra that just ain't right. Your build though each to his own. Good luck with it which ever you go.