Okay, I killed Mr. House, I still have the platinum chip, and I want to bring the NCR to power in New Vegas. Is there any way I can do this?

Do the NCR questline which begins when you do the quest "Things that go Boom" given by Ambassador Crocker.

Is that the one where you have to get the Boomers to side with you? Yeah, I've done that.

Talk to the Ambassador about doing the quest with Freeside.
Talk to the Ambassador about doing the quest with the Omertas.
Talk to the Ambassador about getting tasks from Colonel Moore at Hoover Dam.
Talk to Moore about Great Khans and splitting them up from the Legion.
Talk to Moore about killing Mr. House.
Talk to Moore about killing BoS (I never had the option to get a treaty)
Etc