Originally Posted by
JDNSW
Only from the uni back to the diff, (note that early 80" have a completely different half shaft with a Tracta joint not a U-joint) but easier to swap the whole shaft. Note that lwb and late swb S3 have 24 spline outer ends and have matching drive flanges, so if your S3 has these and you are using the S1 half shafts you need to use the S1 drive flanges.
Note that the top swivel in the S1 had spring loaded taper steel/bronze bush replaced during S2/2a production by a straight railko bush and thrust washer - a much improved system, that the S1 setup is best converted to (unless you are a stickler for originality).
John