What tool do I need??

I am trying to remove the brass mounting nut from the underside of a widespread faucet in the bathroom. There is not much room under there and I was unable to take the nut off with a regular wrench. I tried a basin wrench, but again there wasn't much room to get the basin wrench in around the nut. I also bought the RIDGID faucet installer tool but the valve is too big for the shaft of the tool so I can't even get the tool up to the nut. The nut may be around 1.25" and the tool is 1 and 1/16".

The plumbing is probably about 20 years old(original). What tool do I need?! I am not sure how they even installed the thing! The only way I can think of is that they installed them on the sink and then laid down the sink. I do not want to remove the sink! Not sure if this is a small project or what. Is there some type of slotted socket wrench out there? I see shower valves that are 1 to 1.5" that would work for the spout nut, but the hot and cold nuts have valves out to the side, so there needs to be a slot. Should I buy a shower valve and then cut a slot?(Don't have any metal cutting tools though)

Thanks!

On some, you loosen the trim piece from the top and the whole thing comes out that way. After 20-years, though, it could be corroded in place and tough to break loose. If you can post a picture or know the brand and model, someone can probably help more.

Update: I was able to get the faucet out with a lot of elbow grease haha. But I still can't really access the hot and cold nuts. The nut I pulled off was about 1 and 3/16".

Unscrew the chrome flanges from the top, then the nut under that.

We NEVER install that faucet from the bottom, other than the spout. There are either nuts under the chrome flanges or the flanges themselves are holding it in place.

Ok that makes sense, I will try to remove the chrome flanges from the top, I guess they will somehow unscrew?

You can unscrew the top chrome flanges. CCW off. The lower nut below the lav never comes off, it's just to set the height to the lav.

That worked perfectly! Thanks!!!