The last time I got involved with these extremely low production Corvettes, I was threatened by an owner. I'm not sure I want to say too much about the 1966 L-88s other than the fact that the one Dick Guldstrand picked up in St. Louis for Roger Penske was a true L-88 (with aluminum heads) and it met the F.I.A. homologation paperwork. That was a special Corvette.
I think the jury is still out on the M-22/HD427s. I'm not going to say how they were delivered from the factory, because I don't know.
The RPO L-88 (with aluminum heads) was not released until March of 1967, as testing was still being done on the prototypes well into the fall of 1966.
That's what I put into my book.
Dr. Pete
www.corvetteracinglegends.com