69 Dart rear frame issues

So I am still in the process of frame and body repair on my car. The car looks like it was hit in the rear on the passenger's side. The rear pass. frame has a kink right above the axle hump and also has some rot. The driver's side is also rusted pretty bad. Also the PO welded the leaf mounts to the side of the frame in a totally different spot..... Should I replace both or just back half the car? Both rails HAVE to be replaced. Plans for the car are a street/strip car. Car was tubbed and will be tubbed again. I can get the bare back half set up for 4link for around $600-$700 or both rear frames for around $760 @ AMD. Thanks in advance.