Need some help with turn signal switch

Not hard, just make sure your wheels are straight and mark the center shaft / steering wheel before you pull it so you can get it back on straight. If it's not a daily driver I would open it up first before ordering anything. Might be an easier fix and the mechanism has just loosened up, but I would imagine one of the tabs is broken and will need replaced. Search for a 70 Dart turn signal switch on ebay, might just have to take your chances on a Dorman cam switch, doubt you will find any NOS ones reasonably priced.