Tri-X and FP4+ account for 95% of my film usage - I have found that Rodinal with Tri-X produces far too much grain for my liking (6x6 negatives, 1:50 Rodinal at 8x10 prints with grain) but Tri-X in D76 1:1 is superb, in tonality, sharpness and grain control. If you plan on shooting it at box speed (400), you might as well shoot it at 800 as there is no difference in development times and very minor shadow loss. However, I shoot mine at 200, usually add 1/3 stop for the yellow filter and it comes out wonderfully with very robust shadows. The sheet film is a completely different beast and works best shot much closer to box speed, again with D76 1:1, in order to exploit its' tonal curve to the max.
Ralph, if your supplier is out, is it just a temporary (1-2 week) problem and this is an urgent project? Otherwise, "dance with the one who brought you" (i.e. wait for your supplier to restock or order online).