Preparing concrete block opening for exterior door
I'm in the process of replacing several exterior doors, and one opens from my basement to a stairwell outside. The wall is constructed of 8" concrete block, and the old door was installed with a buck (outside framing against the block) made of untreated 2x10. Removing the old framing exposes the concrete block on three sides (not on top, which is wood framing). The sides I plan to install pressure treated 2" framing with tapcons. The bottom is where my questions arise.
Previously, there was about 2 1/2" of poured concrete sill below the door. I've chiseled/hammered out the sill, exposing the block underneath. This makes the bottom of the rough opening virtually even with the outside floor at the base of the stairs. (There is also a drain outside at the stair base). I suspect the concrete sill was raised to prevent flooding from a flash rainstorm, etc.
Should I be pouring a new concrete base for the door which the pre-hung steel door will be mounted? Or, should I use pressure treated wood for the door, and finish the outside with concrete, as there will be a few inches extra where the aluminum sill doesn't reach the outside wall?
Any advise much appreciated.