Will this bolt straight into my truck without any modifications?

Yes. This tank mounts at factory points—no drilling, no brackets to fab. Drop it in where the old one came out.

Do I need to flush my cooling system before installing this?

Good practice to flush out old coolant and debris while you have the tank out. Prevents gunk from settling into the new aluminum unit and extending its life.

What about hose clamps and fittings—are those included?

Tank assembly only. Reuse your existing clamps and hoses if they're still good, or grab new ones while you're at it to be safe.