The simplified answer is - you can't, you will have to set up pairs of cameras and render them individually. Other than the logistics of managing two sets of renders (which you can use the Batch Renderer to do, for example) this yeilds the same rendered result as would a special "stereo camera" would do.
Note: The 360 VR camera case is special, because there is no way to just take two spherical cameras, and get proper spherical stereo. The standard spherical camera shoots from a point, but a stereo spherical camera actually shoots images from a circle, with the eye rays coming out tangentially from that circles left and right "sides". This needs a special shader to accomplish and is impossible to accomplish by just placing two "regular" cameras.... whereas regular stereo can be easily achieved with two "regular" cameras side by side.
That said, someone may in the future write an Arnold camera plugin for "regular" stereo, but as of the writing of this reply, no such plugin is known. If and when this happens, this can easily be used in MAXtoA using the same scripting frontend trick as the panoramic stereo camera is implemented through.
