A solid Step 1 score, and if you do as well on Step 2 then you should have a good app.
Unfortunately though I believe if you've already graduated from med school then rotations might not be possible, only observerships I'm afraid.
However fingers crossed you should be able to do research somewhere. But first things first. If I were you, I'd pick one specialty and try to focus everything on getting into that specialty. Especially as an IMG, you can't afford to be too divided with regard to specialty applications. The hardest specialty to get into of the specialties you've listed is probably radiology, although radiology is currently on a downward trend. But it still has the haze from the previous decade or so of being a competitive specialty so many PDs still think this way. All of the specialties you listed are hard if you aim for top tier places of course. IM and neuro are probably the easiest to get into of the ones you mentioned, if you are geographically flexible and happy to get into community programs too (although if you want IM then fellowship, definitely aim as high up the academic ladder as you can i..e academic/university programs). Anesthesiology isn't super difficult either, and is also on a downward trend. But it's probably slightly more difficult than IM and neuro. Anyway point being I'd definitely focus on a single specialty, especially as an IMG, rather than spreading yourself too thin.
Next I'd pick a city you're interested in living in, hopefully one with a solid academic center with teaching hospitals etc. Then just email physicians/profs to see if there are any research opportunities they might be willing to bring an IMG on for. Sorry, this isn't very helpful advice, probably common sense. Maybe others can better advise you as I haven't actually ever looked into how to obtain research positions post-med school. But this is hopefully at least a start. You might be able to ask the physicians/profs for advice as well, even if they can't offer you a position. People are usually pretty helpful in my experience. Regardless good luck to you!
