The rebuild has begun

I've had this 74 Duster for a couple of years now, and it has been a great driver. With a slant six and a three-on-the-tree it's no power house, but it's good for just cruising around and getting looks.
Now, however, the encroaching rust has gotten to the point where I need to stop it before it gets too much worse. So as long as I'm doing body and paint, why not upgrade performance as well, right?
I took the six out yesterday (still runs great) and it will go into my 74 Scamp. Then it will either be my driver, or maybe get sold.
I have been planning to put my 1963 413 in the Duster with a 4-speed and a 8 3/4. Now I'm not sure. I have several engines to choose from, and am hesitating on which to go with.
My choices are:
73 440 - its in pieces and may need major block work since it has been rusted over
67 383- engine is complete and supposedly ran when it was pulled
70 340- engine is complete but has corner of casting broken off where it bolts to the trans. I don't know if this is fixable or not
86 318- complete and was running when I pulled it out of the Diplomat
No matter which one I choose, it will need to be rebuilt, so it's just a matter of deciding what I want to drive, since the money will end up being about the same on any of them.
So, that's the basics of the project. I won't be doing much to it until I get the Scamp on the road, but at least it has begun.
Here are some pics, so tell me what you think.