Were power windows availble from the factory with a "standard" interior, or was it deluxe only?

Also I'm intrigued with the "Fold Down" rear seat. Can it be installed in a convertible? What parts/modifications would be needed? I had a '73 Nova Hatchback that had a fold down rear seat, and I've seen a few Novas and their cousins in boneyards...anything interchangeable/usable for a Camaro rear seat swap?

I don't think that power windows were limited to delux interiors. I do know that the can be installed in a STD interior 69 convertible because I did it. The nice thing is that the switches can go in the same location as the manual crank holes. They just need to be made rectangular and the metal trim pieces installed. Fold down seats will also fit the 69 convertible. The hard top fold down seat is the same width as the normal convertible because the fold down seat came with armrests. Brackets need to be welded to the floorpan, I suppose they can be bolted in. They are readily available from parts suppliers. There is a sheetmetal rail that welds or screws in along the lower back of the floorpan between the passenger compartment and trunk. This piece holds the cardboard divider in place. Then the latch and rubber bumpers screw in. Be sure to get the trim pieces that fit around the bumpers from your donor car. If you need to re-cover the seats the bottom cover is the same, the back cover is special for a fold down seat. An upholstery shop can fix this if needed, If you buy the proper covers they are not too hard to install.

Sounds easy enough. But I haven't seen any Camaro fold-down seats in a junk yard EVER! Since you say the convertible seat BACK is the same width, am I to understand that I can make the modifications to my existing back so it will fold down or is there some special seatback frame I need to get my hands on?

Also are any of the parts from a '73-79 Nova, Ventura, Omega, or Apollo hatchback fold-down seats of any use to me in this quest?

I'm not sure about the Nova style rear seat. sorry, I missed that point in your first message. I haven't even seen a early camaro in a junkyard for years. But I do know the fold down seat has a different frame, with hinges, a back and latches, so you cannot convert a convertible seat. Try to get a good look at the camaro seat, maybe at a car show, and then compare to the nova.
good luck.