I recall reading many manga/one shots with sex/soul change, and I realized that most of them were actually hentai
The somewhat limited but maybe-fits-your-requests suggestions (not hentai):
Kashimashi - Girl Meets Girl is about a boy who is turned into a girl due to an accident. Its a short 3-way romance commedy series which should fit your criteria. Unless you are put off by yuri-ish themes. Not really swapping bodies, however.
Pretty Face is also about a boy who got into an accident, and had a surgery in which he ended up with the face of the girl he loves. I forget if he ever gets a full body change, but do check this one out. This one is also not swapping bodies.