I install mine with the rear wheels on the ground. With the engine dolly I use and the lift holding the car I've found it easier to install the trans cross member on the trans first and then use that as your first point of contact as the body is bring lowered down. Put those 4 bolts in and that helps align everything else. Come down a little lower and catch the 2 rear K frame bolts and then down a little more for the front two.
Tighten the 4 K frame bolts and then use the lift to bring the car back up and set on jack stands.
It literally takes 10-15 minutes.