i am about to start working on one,
here is what i think i am going to do
I cut my swing arm in front of the shock mount.
get a 2 17.25" 1.75"x1" rectangle steel - This is to slide into the swingarm and will touch the front and the back weld that into place, this should make the arm a +4
then get another 1.75"x1" rectangle steel that is about 7" to make a new shock mount - Cut the ends off of it so it looks like an L on both sides and slide that in between the swing arm and weld it into place.
just my idea, all i have done so far is Cut the swingarm, going tomorrow to get the steel.