I added the VQ sear to my KMK678GC Slabside without adding/changing any other internal parts. That one part alone dropped my trigger pull down to 33 ounces (2lb 1oz.), but my trigger pull was a little under 5 oz from the factory, so yours might be a little more than that. The whole VQ kit is only supposed to take it down to 2 1/4 lb.
One thing to note is that the VQ sear also shortens the trigger pull. You will have to go back in and adjust your overtravel screw after you install it.