Read the book, The Mummies Of Urumchi, Dr Elizabeth Barber makes a direct connection to the mummies in the Tarim Basin to the Celtic/La Tene people around Hallstadt, Austria. In fact, chapter #7 in her book is titled, Hami (NW corner of Turfan Basin) and Hallstatt
And, Dr Victor Mair/Dr J.P. Malloy make similar connections in their book, The Tarim Mummies.
I've not read the book indepth, -- just glanced through it at the library, but what I do note is that it's not easy to define a Celtic physiology as distinct from, say, a Germanic or other Indo-European/Aryan group. Hence, you'd have to base it on linguistics and the evidence does not seem to define that Tocharian was any more related to Celtic than to Iranic-Indic etc.