To be honest with you if you have any fabrication skills, use bike TBs, a megasquirt ECU and don't mind having a dig round a scrap yard for the right bits you could do a TB conversion on a zetec for £400 or less.

Bare in mind though what you save in money you will have to put back in with your own time.

I would want at least 175bhp out of a zetec on TBs with a decent exhaust manifold.