Were Trailing Arms an Option?

[jim-bob]

..got a 67 GMC Short Stepper (No Eng.or Trans yet)
There are no Trailing Arms and no mounting brkts on the axle nor the cross member..it has the leaf springs now..I thought all the 67-72 were factory installed but I don't know whole lot..So are they a factory option or dealer installed?
Anyway I do want them installed after the frame is blasted and painted..(I'm just assuming that I want them based on some post I've read..Is there something better?
I would appreciate some advise/ suggestions on which way to go in buying them and brackets..Should I look for used ones or new ones..Is there a template for welding on the brackets? IF i lower the trk at all it will only be 2/4..Your help will be very much appreciated.