Found this on eBay while looking for details of a mid-engined Rover V8 Chamois (long story); ironically a modern interpretation of what I was looking for.
A '65 Singer Chamois with a Subrau flat-four turbo lump from a '92 Legacy, mated to a VW Type 2 gearbox. Looking at the ad, a lot of fabrication has been done, but then again there looks like a shedload more to do. It would take a brave man to bring this to fruition, but boy what a car you'd have at the end.
Who's gonna be brave enough?