Chris on the grape vine Ive head of twim cam heads for the A series from Factory.
Only 2 or 3 where made from sand casts and some people have a hold of it.
If that can be somehow lent to you or bought then you can either use it for your
mock up or just use it for yourself :) Im not sure where they are and if anyone
would let go of such rare items though.

The honda blackhawk cbr1000xx head Simon used is not far off as most of the studs fit
however needs custom timing mech/case and electric water pump at minimum unless you
can modify a vw 4 golf one or use a custom billet one. The original oiling could be
used keeping the original cam machined down to work for the oil and dizzie if budgetting
or use a megajolt or megasquirt setup for ignition.

When I went to Vic Motorcycle wreckers the bloke there had vividly in his scone how Simon
came in with a A Hgasket, tried several heads when bang the CBR one was so close.

Its alot of work but who knows you might be able to use a cbr head as a reference?
The only thing I would change about the bike heads is how the exhaust curves down
to far to suit the bikes where they could also be angle up for better auto headers
resembling the formula 1 spaghetti style setups.

If I could go back in time (just ten years) I would have used RMITs equipment to
make a ga16de alloy block that suited a hayabusa head and directly to a t5 box.