Interesting conversion kit from Lynx AE for a mini subframe so that you can fit a Yamaha R1 engine into an EXISTING mini subframe.....rather than get yours converted. This enables you to switch back to the A series engine if you wanted to. Comes with a reverse too.
A doddle in a Mk1 or 2 I reckon.
http://www.lynxae.co.uk/Products-MiniR1.htm