what is the proper way to set the tightness of the spindle nut on a 74 valiant. i am doing a disc brake swap

You need to get the torque value from your FSM but the general procedure is like this:

Tighten the nut to the specified torque. Place the slotted locking cap over the nut so that on set of slots aligns with the hole then back off the nut one set of slots and install the cotter pin.

In '62 the torque was 90 in-lb for a Plymouth ( B-body ) and 70 in-lb for the Valiant (A-body); yours may differ.

_________________
David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

In 1976 it became 'tighten the bearing adjusting nut' to 240-300 inch pounds while rotating the disc and hub' check runout, then back off to release preload, then finger tight , put on lock nut, then cotter pin...

-D.Idiot