383 into a 68 Valiant

One of the mags built a 67 Dart with a Stage 5 Hemi headed 440 years ago.. it actually wound up weighing something like 57 pounds LESS than the /6 car did.. ain't technology wonderful?
Dug up the build your own Big Block K frame article I was talking about..

http://www.bigblockdart.com/techpages/dck.shtml

The Schumaker mounts would be the way to go unless you are or know a good welder.. either way will get it done.
Alan