Ordering a new L78/L89 Camaro/Chevelle

[mockingbird812]

I was looking through my original '69 Chevelle brochure dated sometime in Jan/Feb of '69 and there is no mention of the RPO L78/L89 motor option (only the 325/350 HP). Same thing with magazine ads that I have. I have heard of these motors referred to as "special order". What would a dude have to know/do to get one of these motors in his car from the factory. Or, did they later include them in advertisements/brochures/etc.? I realize that the solid lifter motors had been out for 4 model years (starting with the Z16) by that time, but am curious why they would not advertise this better.

Thanks,
Sam