I've got SEVERAL friends with modded 5.0's and they can't even keep up with my friends stock LS1 in the 1/4. You could have had an especially strong one but most of the ones I've seen were 15 second cars stock. They only had 225 HP and were rather heavy. Ford tends to overrate their motors anyway.
"Ahh, to have the pos 323 appreciated by a 30k evo owner." -SactoTodd