willa 66 b body rear end housing and axles fit in a 73 dart swinger?

Yes. The spring pads need to be moved inboard 1/2" per side. I have a 67 Coronet 8 3/4" axle in a 67 Dart. I have 15x6 wheels on it.

will by stock ralleye 14 inch whhels work?

Since they are narrower, yes.

Some will not even move the spring pads. I heard of people just pushing the springs out. Pretty butch and I'd think/hope one would only run rubber bushings. The slight twisting Would add a little Spring rate.

Not a good thing for logivity of bushings or springs. But not like people are putting 15K/year on these cars anymore.

Not sure if you could move the front brackets in that much even if you redrilled the 4 holes and used a thin head main transverse bolt & installed it from on the inside so it would be sandwiched inbetween the bracket & the frame rail so the bracket could be moved in as far as possible. the rear shackle might be doable either by moving it or using offset hangars. Just a thought to keep everything lined up & a 1 minute look see would answer that possibility.

I put one in a 67 Dart without moving anything. Car went straight and no traction issues, but wheels are limited unless you use custom backspacing.

I did the same years ago. Ran 13.80's on street tires. Woo Hoo not bad for a street car in the early 70's When I added slicks at the track I lost over a second on my ET with the slicks, 14.80's I repeated the scenario several times at Fremont drag strip.

At 19 years old, I was Depressed and Totally baffled as to how I could go so much slower with slicks,
My mentor came to the rescue as I was FINALLY ready to listen to him. We redid the rear suspension aligning the springs and hangers, rebuilt the front end (which it needed).
The first pass on the same slicks netted a 12.65 with no other changes. Bolting the street tires back on netted a 13.20.
He explained to me that the rear suspension was binding due to the spring alignment, which in turn was further complicated by the sloppy front end.
I learned a lot from him and I hope he is smiling from above as I write this