Looking for a replacement half shaft for my 1978 automatic...does anybody know what years will fit? Help! Thanks!

Do you have an R180 or R200 differential? The R180 has a vertical rectangular looking diff cover, and the R200 is more rounded.

its got a r180

In that case, you'll need to figure out if the half shaft in there now has a flange or an side yoke assy. At some point in 74, the factory changed the half-shafts to include an side yoke assy that gets inserted into the diff to speed up the assy process. This allowed the line workers to simply insert the completed half-shaft with side yoke assy into the diff and attach it with a single bolt, rather than having to bolt the inner flange of the half-shaft to a matching flange on the diff with 4 nuts and washers. You can see the two types half-shaft ends in the attached picture.

My guess is that you have the later type, but in either case, you should be able to use any half-shaft from a 240-280Z, but you'll only use the portion outside of the inner u-joint. You can just leave the side yoke bolted to the diff, or pull it out to make assy and re-attachment of the half-shaft a bit easier on yourself once you're done re-assembling it.

Hey thanks Enigma! Very helpful!