in great confusion vs head over heels

in great confusion and head over heels both are adverbs.

Word	Noun	Adjective	Verb	Adverb
in great confusion	No	No	No	Yes
head over heels	No	No	No	Yes

As adverbs, in great confusion and head over heels are synonyms defined as:

Other synonyms of in great confusion include heels over head, topsy-turvily, topsy-turvy.

in great confusion (adverb)	head over heels (adverb)
in disorderly haste	in disorderly haste