Well, you are thinking of the loads in a little different way.
A coil spring is nothing more than a coiled up torsion bar. The sway bar arms are equivalent to the ends of the springs dia which cause the spring metal to twist like a sway bar when compressed.
You are not allowing for the added travel shared by the remaining coils, they will not only be loaded more per coil but will be compressed more for each coil than before.
If you take a 300 lb spring and cut it in half, you will have two springs with 600 lbs rate PER INCH OF COMPRESSION each.
That is due to the remaining coils being compressed twice as much as before, half the number of coils are recieving the same load and travel as the whole spring did.
In other words, the inch of compression you would use to "rate" a spring is shared by half as many coils as before.
The end coils don't contribute as much to stiffness, so cutting off the first coil doesn't make as large a change to stiffness as the second coil cut does on a Camaro spring.
Hope this helps.
Check my web page for First Gen Camaro suspension info:
David's Motorsports page
First Gen Suspension Page
67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Chev 350 Can-Am Vintage Racer