I have an '89 Classic, and I am running HD in the front and rear. I have yet to notice a height difference between the front and the back, but I can honestly say there is a bit of a ride difference. It now rides more like a truck- you feel the bumps a bit more. I love the HD though because when I go up to Canada fishing, I have the truck full, stuff on top in my rack, and I am towing my 18 ft Lund which weighs a ton, an the back does not sink much! It still rides smooth, and handles decent in the turns even with all of the added weight.
As for a lift, the HD give you a 2" lift by default I believe; at least that's what I got. You can safely go 2" with out replacing brake lines or radius arms, etc. so if you want a bit more height, I would reccomend getting the lift.
I am also currently running the OME shocks too ( I got a good deal on the combo) and I believe that the combonation of the shocks and springs is great.
I hope this helped some!
Jeremy