You should look in the Straight websites and Straight pictures and videos forums, as there are already threads dedicated to black/white sex.
As for stories, the first time I was with a black woman, I was not her first white guy, but she complimented me on my erection and said I was up there with the black guys in terms of size. I lasted quite a while for a first encounter, with all the excitement of being with someone new. We changed positions multiple times after going for many minutes in each one, finishing up in missionary, with her legs wrapped around mine.
After I came and lay down next to her, she said what a great fuck it was, so good in fact that she actually had an orgasm. She said she rarely cums from intercourse alone and that I fucked her so well she couldn't help but cum. Since she was the first woman I was ever with that could have orgasms from vaginal intercourse, it was a very satisfying moment for me.