Newbie Dart Axle question

Hi all, thanks for the input so far. Found a site that stated that the early and later 7.5's had different bearings or something and the axles were different all together and not swappable.

Was set to do the swap of the complete 7.5 for the complete big bolt 7.5 when I lucked into an 8.25 complete at the local self serve wrecking yard. It is an open rear, but it does have 3.21's in it. From what I've seen that must have been a pretty popular ratio. Anyway, it is out of an A body so apart from shortening the drive shaft I should have a bolt right in.

Thanks for all the posts.
Cheers