ok not to bring back the Sidewinder talk but AAM's are relitivly new for helicopters they only realy were introduceded around 1990's
so the when it comes to retro fitting a weapon onto a helicopter it is a little hard but afaik the Longbow has sidewinders being it entered service in 1993 or so, so if you are going to use Hawks scripts (the one from his Ka-50 and modified DKM Mi-28)or one like it you should lable seperate 1990's longbowand call it AH-64D 'Longbow' 90's or somthing then have the normal AH-64D 'Longbow' and add sidewinders to the loadout
but if you are not using that type of scripts then dont worry and just add the sidwinder varrient because it is a official loadout and only recently have they had a chance to use them i.e. Afganistan war and the Iraq war