will theses K-members work..

I have try'd looking and I can't find what I'am looking for...ok here it is I have a 73 plymouth duster It has the slanted 6 K member. I have a small block K member out of a 70-71 Dart. I have another buddy with a big block K member out of a 68-69 Cuda. I was woundering if any of them 2 will work in my 73 Duster..

I would like to go big block and use the right K member instade of using motor plates. What ever one will work in my car I will go small or big block..Thanks Jimmy.