I think I already mentioned that you can buy flanged axles cut to the length you need. This is in some ways your best option, they are new axles and you have to get them sliced of at the required length.
I am sure that the later bearings and seals do fit the early housings. But I am prepared to check that out if necessary. Sure, the early axles used different bearings and seals, but that was to do with the axles not the housings.
As I mentioned previously, you will need to get the bearing adjusters etc from the later model axles to fit onto the new axle shafts if you go this way. I am assuming you will take the advice to not use green bearings.
Also, the Sure Grips had the same internal block throughout, it is only the open diffs which changed sizes.