The engine will work. It's just like any small block and they made 1964 A-bodies with 273's and the 360 magnum is the same size.
You cannot use your existing push button trans from a slant six with the 360. The bellhousing bolt pattern is very different.
You could use a factory V8 push button transmission if you can find one. You would then need a flexplate balanced for a 360 magnum, as the 96 Ram one isn't quite right and the balance weight is probably on the converter in that year.
