[randy500]

I have done the switch a couple of times, I always change the complete crossmember with brake lines intact.
Drum brake crossmember had the metal tab for the brake hose in a different location and I think it is generally just different.
Yes you need the proportioning valve and the lines to the master cylinder. Get both front and rear lines and unhook the rear line at the connection just behind the crossmember on the passenger side. It should screw right into your existing rear line.

If your considering drop spindles then maybe its not such a good deal, then you just need dust shields and center link then all new tie rod ends and adjusting sleeves. If 73 and up stuff is cheaper then use it, the outer tie rod is different as well as the upper ball joint.