Rear Spring Swap

Sorry to hijack, great thread, looking to do the same in the very near future on my 69 barracuda ragtop. the springs and rearend are out of the car while other work is being done, I noticed I need new rear shackles and bushings, and may as well look at new springs too...any suggestions?? FWIW, its an "S" car, so has HD supension.

Thanks
4spd