I have the 204s in my 103, and ride very close to the same as you do. Go out and compare how the bike accelerates in 6th gear from 60 and 70mph. My bike accelerates from 60mph like your does from 70mph. Thats the difference you will feel. The 48s may be a bit stronger but will fall off sooner on the upper end. I believe its the 54s that have the same timing as the 204s only with higher lift to match the new heads.