66 Dodge Dart GT- Deep Sixing Slant 6 and Automatic for late model 5.7 or 5.9

There is also
HemiDenny
www.moparsuspension.com
But yes you can use your original k frame. You just have to be creative. And expect some trial and error with parts such as exhaust manifolds.
Here is a link of an early dart 5.7 build.
Tincup's 63 Dart w/5.7 Hemi