I need a new k frame. 74 dart

Contact the folks at CTC Auto Ranch in Denton, Texas. I once bought a complete '72 & up K from them that enabled me to rob a bunch-o-parts for a disk brake upgrade on my '68 Dart. They are NOT cheap! But, if you're in a pinch you might not have a lot of choices.
www.ctcautoranch.com
Their web site doesn't come close to cataloging all they have in those acres and acres of cars. You will need to call them and tell them what you're looking for. They are usually very helpful over the phone. They can ship economically via motor freight.