Was able to determine it's from a CB175 twin (I'm pretty sure, based on pics and measurements). New float on the way.
I have had the bike running fine with this carb, without the intake piece. Although I don't think it's a rubber boot like on my 550. This carb isn't a spigot mount.
It was bolted right up onto the head when I got it, but looking at the parts diagram, it looks like there's a metal intake piece. What are the complications of running it with the carb bolted right to the head?