For your black border, use a mottled/marbled black. The differences in black wouldn't be as noticeable. (Oops, I see you've already bought the fabric.) Bright colored variegated thread would be great for quilting--it would tie in with all the colors in the logos of the shirts. I assume the recipient is a race fan or does he actually race?
I made a memory quilt for my brother several years ago. He's a former midget race car driver. I used some T-shirts and photos of races/trophy presentations/etc and sashed/border/backed it with several different sized black/white check fabrics. It was a fun quilt to make and he LOVED it. Wish I could find the picture to post.