A very interesting website for those who haven't seen it:
http://mk1-performance-conversions.co.uk/mk1_index.htm
Full of LOTS of historical performance tuning accessories and the like and a lot of old BMC brochures and competition correspondance etc etc.
Quite a few performance heads (7 & 8 port heads and alloy heads) are mentioned as well no Elder heads though
(might not be old enough).