No, Atlas did not do unpowered units, just powered ones in both 2 and 3 rail.
With the excellent part range available from Atlas for many years on those units, you could have created an unpowered one in kit form, though whether that would have been cost effective compared with buying a discounted complete unit is a question. If one were doing a dummy, though, you'd have that heavy metal frame to drag around, and I think you'd want to remove the internal gear towers.
They did do the undecorated kit in all four [ AEM, ALP / 2R, 3R ] variants though.
SZ -- who thinks the cross-pollination agreement between MTH and Atlas might make an ACS-64 more feasible......