Greg63, measuring is advised. Recently there was a post on this subject where someone put the later axles in (like hoppa, above) and they fit, sort of. by that I mean that, on closer inspection, the axles were sticking further out, a fact that was hidden by the wider brake drums. the bearings were obviously riding on a different place on the axle but were still working. pictures were posted of the brake drum/backing plate of the mismatch and of the correct axle/housing, but I can't find the post, sorry.
I don't mean to imply the hoppa's axles aren't the correct length, just that there's this other possibility.
found it:
http://67-72chevytrucks.com/vboard/s...d.php?t=390680