Coil Spring Confused

[HustleRussell]

I'm installing a big block in my 68rs. Not sure if I installed correct front springs. I've referenced the 69 chart.

http://www.camaros.org/images/pages/chassis/69_spring_chart.pdf

I did the math just like the example. Came up with the same springs "HA".

But why does the 396 coupe listing start off with EY, YH because the lightest weight 396 is adding more than

133lbs?     I'm I missing something?