Many thanks to Dr. Bodiford and Dr. Goldsbury for their detailed and well-sourced insights into this question.
For what it's worth, here's a shot of one of the four gates to the Great Stupa @ Sanchi. It has an extra cross-beam, but nonetheless, the basic homology is there.
There's also been an analysis of the Great Temple at Nara (which I can't lay my hands on just this second) showing that, although the construction is wood rather than stone, the proportional spacing of columns is precisely the same as a number of Greco-Indian precursors at the other end of the Silk Road.
And taboos or no, there are a number of Japanese researchers who have started to look at the question of Silk Road Culture because of intriguing but not quite definitive correspondences like these.
Anyone interested in a broader if somewaht tentative look at some of these underlying questions is welcome to look at my current draft of Part I of Tantric Actors on the World Stage: Curtain Call or Final Act.
Part I takes a look at the dissemination of tantric iconography and associated cultural patterning along the silk road, particularly in the period 600-1000 CE. Part II, which is still too rough for words, will take a look at modern implications through the twin filters of HHDL's dissemination of the Kalachakra Tantra and the rather less happy consequences of Shoko Asahara's crypto-Buddhist Aum Shinri-kyo.
Just drop me a pm and I'll send it along to anyone who wants to suffer through it.....
Fred Little