HID ballast replacement w/ aftermarket?

So, after changing out my D4R bulbs, I've come to the realization that the ballasts have become weak and will not keep the bulbs fired up. I have about 4 or 5 pairs of aftermarket ballasts from different HID kits that I have had over the years and some I kept as spares. I was wondering if anybody has utilized these ballasts as an effective replacement for OEM units as they are significantly cheaper to get and replace. I know off the bat a mounting plate would have to be fabricated, but that isn't anything super difficult (I have a bunch of 18 ga sheet steel laying around). I just wanted to know if anybody has done this and how would get power to the ballasts since these units use a 9006 connector to power it up.