I also have a 416 making 450whp on a mustang dyno nothing impressive, sleeper cam 230/234 602 602 117 lsa, stock intake. 10.4 1/4 on hp leaving off idle with a 1.41 60ft. You are making 500-515whp through a 3800 stalled auto! I would be happy take it to the track run in the 10s. Your setup in a m6 car would make 525-540whp all day. Nothing to worry about.
Your numbers are excellent especially if the converter was unlocked during the dyno pull. Take it to the track those are the only numbers that really matter.