As Gino have mentioned, Dragon/DML has produced 2 US GI kits for Korean War Era. However, that Pusan Perimeter would be near impossible to find these days (at least I haven't seen that kit for ages). You can also try Verlinden or Jaguar. I also have built quite a few kits dedicated to Korean conflict and I ended up using Tamiya or other DML kits to convert them to fit more into Korean conflict era.
Good luck and keep us informed with your progress.
504th PIR - Devils in Baggy Pants