You are correct, you can use the scarebird brackets and napa parts for their conversion.

You can get a big block 727 pushbutton transmission also called a cable shift transmission from big block powered 63, 64 or 65 B body cars and C-body cars like Chrysler Newport, Newyorker, 300 and Imperials.

The best transmission to find is a 65 cable shift 727 trans. It has a slip yoke on the end instead of the companion flange or ball and trunion joint like the 63 and 64 transmissions do. The slip yoke will handle a lot more abuse than the 63-64 companion flange will. 65 cable shift trannys are getting hard to find and expensive, it might be cheaper to use a later big block 727 trans and the Imperial services cable conversion kit in your car.