JT,
I have a 42" oven and I can't imagine it being smaller.
And I'd have to agree with the wise Canadian. You can't go backward much more, but you need a bit more landing to accomodate your chimney vent if nothing else. Cantilevering out would have been easier when you did the original pour, but you can still do it. Just rebar into the existing slab and pour the landing itself at floor height.
The polished concrete done by Balty is gorgeous, I'd imitate it:
