I am not sure you want Heavy Duty springs.......the 412 shocks are likely made for larger/heavier bikes than the Savage.
I have 412 shocks on my Cafe', and the standard springs (120/170) were too stiff. I ended up ordering lighter (105/150) springs and the ride is much better. I do believe the valving could be a bit too heavy for the Savage....the small pavement ripples are pretty noticeable, bigger bumps are handled pretty well.
My bike weighs 320, I weigh 170.....probably more like 185 with my gear on and ready to ride (My boots are heavy

).