All IAPs do need to run the same version and the latest is 6.2.1.0-3.4.0.1.
Will the 175s be connecting wirelessly via Mesh or will they be wired? If Mesh, you might connect them wired first so they pick up their configuration via the wire then bring them up via Mesh.
I would also suggest taking a look at our "Outdoor Validated Reference Design Guide" for helpfull information on antenna orientation and alignment.