The lift height should be the least of your worries. You could compensate for that with different shackle lengths and mounting locations, but that is assuming you are not looking for a simple way that just involves bolting a couple of shackles together. I'm not a big fan of that style of suspension anyway, and even the picture of the Springer has more to it than simply two shackles bolted together....same basic concept but has stops for upward travel and such.
If you really want something like that, why not just buy a set of Revolvers (again, I don't like those super-droopy uncontrolled suspensions...but maybe better than slapping other stuff together).