Welcome to the forum
I am impressed with what you have done with your truck, especially since you are in France. I'm sure that does add to the difficulty factor.
What transmission will you use behind your 496?
I do not know the torque specs for the control arm shaft nuts, but I do know they are a PITA to get aligned just right. Yes the holes drilled into the lower shafts locate on the pins in the middle of the saddles on the crossmember.