The combination of the Knuckles, hubs, bearings, rotors, calipers, and lower ball joint together is one big heavy mess, probably in the 60-80 lb range. Personally, I'd mount the knuckles up first and assemble from there, especially considering the LBJ has to be assembled first and the taper points up.

For the LCA pins, you'd probably want to use a block of wood and try to bash them in a little bit to get it to stick on the taper until you can tighten.

The whole wheel thing is complicated because of the A-body rear axle...the front track is probably still a significant difference from the rear. After reading your other topics, looks like the Darts have less room in both the front and rear than a Duster. I'm looking to measure with my wheel-rite and probably go with 275-35-18 on 18x9 +35 offset (6.4 backspace) wheels, and maybe a small spacer with my factory 11.75 fronts.