We moved into a new build house with an un-finished basement. I am going to start finishing/framing the basement and 4 steel support posts that run down the center holding the beam. The main beam is 2 - 2X12. The posts that are attached to these beams have plates on the top and bottom that are 4"x6", so they would stick out past a typical 2X4 wall post. Is the standard procedure with these to take the post out and replace with wood? Or do I trim the plates down to work with a 2x4? All but 1 of these posts will be within a wall, the last one I am hoping can be wrapped in either wood or drywall. Or replaced with a 4x4.
Standard procedure is to cover them, not remove them. Those are structural members and cannot be removed without an engineer designing a replacement which will likely be bigger and more obtrusive.
See this on encasing steel structural members in a stud wall.
Those steel posts with end plates are the absolutely first rate product for this structural need, and the design and installation has been passed on by building inspection. They are not to be replaced. Drilling through for plumbing or wiring would require special authorization. I would say do not do it.
If the plates on the bottoms of the posts, or the posts proper, protrude beyond the envelope of a stud wall, then the baseboard (and the drywall) could jog to cover it. The 2x4" bottom plate of a non load bearing stud wall is not under tension and can be terminated on one side of a steel plate, directed around or over the plate, and resumed on the other side.