i used s& w on my car and after dealing with them i don,t think i would use them again cause there are way to many companys that will go out of their way to help you & get stuff ship to you, they was like i'll get it to ya when i can. good thing i didn't need the directions they showed up two weeks after i had my back half installed.
my next one i do sounds like i'm trying chassis works.
if this is your first one i would say to use a pre-welded back-half. i think it would make it a little easier for you.
good luck and remember measure,measure & remeasure.