Cees,
I only know of two surviving in Australia, both are in museums, one is in an airframe, I assume they are few and far between elsewhere, however the BAPC lists 24 in the UK?
I have always thought these to be rarer than rocking horse – s#*t or is that flying horse S#*t – smiles, and I assume the twin re-creation you refer to will need 2 engines? perhaps its better to try get access to one to create a fibreglass casting of the front of the crankcase/nose and cylinders? and build two dummy engines?
Regards
Mark Pilkington