Big fan of your posts, am planning to do some of your wishbone mods soon. Afraid I can't confirm your question, but a couple of years ago had to get our other jtd 10 valve thro an MoT test quickly; one of the outer cv joints had failed, and I seem to recall the garage being very pleased with themselves because although the jtd part was unavailiable at the time, the V6 part was and this fitted no problem....but this was sometime ago.... Short version; good chance the 10 valve half shaft will fit, but very little chance 20 valve is swappable.
Hope that helps - bit surprised Dan or Ned haven't picked up this....is the mighty Autolusso on holiday!?!!
Loving the suspension mods....ever thought about a book on it ' ultimate 156 tweaks '?
On the 10v JTD halfshaft the length between the inner splined section that engages with the diff and the bearing that is supported is different, so won't fit on a V6. Its a little longer. The 1.9 ones are totally different as they have cups & spiders for the inner joints rather than the more conventional looking CV joints that the 10v, V6s and Twinsparks have.
Don't know what your garage did there Cap'n, maybe they just used the inner CV only and removed it from the halfshaft.