Luffy also has the scar under his eye from when he stabbed himself in chapter 1. Oda's design of a 7 year old Luffy has obviously changed since he did chapter 1. This is also reinforced when Shanks and Ace meet and Shanks says that he did not know Luffy had a brother since Luffy and Ace weren't brothers when Shanks was staying at Fuschia Village.
http://read.mangashare.com/One-Piece/chapter-552/page005.html
After looking at this again, a question popped for me. Ace left Fuschia Village 3 years ago (http://read.mangashare.com/One-Piece/chapter-552/page004.html) but yet Sengoku mentions him becoming famous 2 years ago (http://read.mangashare.com/One-Piece/chapter-551/page007.html). What about that first year?