I do hope nobody thinks I am dissenting here...
What I am talking about when I say you can put flanged axles cut to length in is NEW axles you find on eBay and at Doctor Diff etc. Like I have said, use tapered bearings as per the old days and you need to get the bearing adjusters and bolt-in flanges from old flanged axles somewhere to suit.
The later rear ends will be about 2" wider overall, from memory, than a '63.
I am also saying that it might even be better to just do the brake conversion and keep the original axles, but if you're changing from an open rear end to Sure Grip these will be a tad too long.
Ray