For starters Gtr your short 300 hours total time for the FAA ATP. All the info for converting ICAO licences is available on Pprune you just have to look. Alternatively you can do what I did which was actually go on the FAA website and look for yourself. It isn't that hard to read. Alternatively there are many schools in the US that advertise conversion courses. Email a couple and see what they say. Generally the school will even organise your visa's and licence paperwork for you if you commit to a course.