That is very much not a gila monster. I don't know what a chuckwalla is, so I can't comment on that, but both my partner and I (we both lived in Tucson for years) were immediately like "nah, that's not a gila monster". I don't think it's a gila monster.
I don't think it's a gila
I don't have the credentials some of these guys do but I'd say that sure as fuck isn't a chuckwalla. Seems like it's the real deal...
Gila monster. That head shape and legs/digits proportions could never be a Chuckwalla's. Skin looks like a Gilas too.
Sometimes lizards get sick and look thinner than normal and sluggish, I've found some like that.