812 s and 412 s are the same shock, I don't believe the H. D. springs are an option on the shortys, but I would call Progressive and ask, they unofficially beefed up a pair of 11.5" 412 s for me, $37.50 and shipping. I weigh 235 lbs. 3 clicks up for the setting, rides a little stout, but they don't bottom out.
