These really used to be the ultimate in conversions in the late 1970's (The Dogs Dangley Bits!!!)
Originally 1600 Lotus Twin Cam conversions later becoming 1840 BDA (Belt Driven Assembly) Cosworth monsters mated to a Mini Gearbox (Ideally a JKD 4 Synchro SCCR if you wanted it to last more than 5 mins?)
There is a section in david Vizzard's "How to Modify Your Mini" but not really to any detail.
See Jeremy Clarkson Test Driving one on Top Gear - even he thought it was awesome!
I dont think that vid of clarkson is of a ford crossflow. i think it is a JKD or Kad 16 valve.