F41 Rear Springs with 6 Leaves

[9C1Beater]

Hey All...I'm posting some photos of the F41 rear suspension on my 1974 Nova COPO 9C1 police car. I have posted quite a bit of info on the car in another thread in this section, and figured some of you might like to see this car's unusual rear springs.

I took quite a few photos of the rear suspension and was investigating if it was essentially the same as a Yenko Nova when I discovered one marked discrepancy between the two suspensions...Yenko Nova rear springs have 5 rear leaves and my car has 6.

The car has 120k original miles and was ordered by a Chevrolet executive named Rick Mahoney at the Los Angeles Zone Office for use as a high-speed police car demonstrator (it was a "Brass Hat" car...see documents in my other post). He used the car for 5 1/2 months and then sold it to Los Angeles County where it was used by the LA Sheriffs Dept as an undercover car at the West Hollywood station (it still has a shotgun rack in its trunk). It sat undriven in a garage in the Hollywood Hills for 32 years until I bought it in 2017.

It has many GM stickers still on its suspension components, including a yellow sticker on the driver's side with the part number "340399". The outer brackets have partial blue and white GM paper stickers, and the right support rod has a very faded paper tag that I believe says "Special" on it. The left support rod has a splat of dark green paint visible at the very bottom (it isn't visible in any of the photos, but it's there).

In addition to its mostly Z28 suspension components (from the factory), it also has rear drums and shoes from a Chevelle station wagon.

I am curious if these are possibly big block Nova rear springs (even though the big block was no longer available by the time this car was built). The car handles with virtually no lean in very hard cornering, and it rides very firm (almost like a truck when going over freeway expansion joints...no give in the suspension).