Ed- I ran the Calculator. As you said it's for 69 and I have a 68, but it should be close. Here's the boxes I checked: L48, M20, floor mats, console, dual exhaust, power steering, radio am/fm, rear bumper guards, rs package.
Here's what the calculator spit out: Rear spring rate - 73. RPO Spring code - BY. F41 code - BM. G 31 code - BL.
Hope you can help me out based on these codes. Also, with regard to spring rates, does a higher number mean a stiffer spring?
Thanks again, Joe