Two questions (suspension/bodywork)

[energiesource]

Hi, I have two questions about these trucks. with restoring a cab, should i sand down and primer parts before i replace sheet metal, or should i get the whole thing blasted and primered and go from there?

and for suspension, i have a LWB truck going to SWB and it has leaf springs in the rear but i want to switch to the radius arms and springs, can the cross member for the radius arms be switched out or do i need a whole different frame?

[OARNGESI]

Your probally better taking the cab to bare metal before starting rust repair