To the best of my knowledge, the 1.9TD and the 2.4 TD had little more than a new head and injection system, the block remained the same, AFAIK even the multijet shares the same block, with very little (if none) modification from the TD days. The Wikipedia JTD page seems to agree with me on this one. If i were you though, I would take a look at some of the Alpha or Lancia forums, the FIAT 2.4JTDs are as rare as hens teeth, and finding anyone here with that level of knowledge is going to be tricky, where as, on the other hand, many of the Aphas have them.