They were the "factory shop" for the 505 Superproduction cars (at a min).
The prepared the racing heads for the motors. There were 2 types of
heads, I'll call them I and II.
Stage I - biggers valves and porting (the Yellow rally car has one)
Stage II - same as I but spark plugs are on intake side (perhaps for
better access only(?) )
Both of these heads were 8-valve. I have found no evidence of a 16V head,
actually quite the opposite.
I think the car Pat Whale sold had a Stage I head.