Greasy Fork is available in English.
GET script
Fixed version of old get script.
Sends Head Requests to sys.4chan.org until the post before the one entered exists, then submits the post.
Requires 4chan x.
May have to aim earlier depending on the speed of the board/upload speed/image filesize.
"Post Rate" lets you check the speed of boards, useful for guesstimating how many posts early you should aim for.
How to use:
Fill out Captcha
Enter number to GET in Box
Hit Post