Another Front bag setup question

Ok so I have the front suspension torn apart,cut out bumbstops,shock mounts,etc. I'am ready to find my upper bag mount location. Now I know i have to put my suspension parts back on arms,calipers,rotors,etc my question is do I have to bolt the wheels on and lay the truck on the floor to determine where to weld the plate or can a use a floor jack and crank up the suspension wihth the jack? Thanks