What mods? Edit: I found them on the first page. Just for reference, I had an LS-1 2002 Camaro SS with a TSP cam (I think a 232/236 112 lsa and 598 lift if my memory is good), long tubes into cutouts, ported and polished throttle body and a tune from a guy on LS-1 tech and dyno'd 405 through a 6 speed. And 567 rwhp on a 175 shot. Stock heads aside from different springs. You won't hit that number with your mods, through an auto transmission.
If you want a real race against a Mustang, I'd say to go over to svtperformance.com and post on there that you can put 1 and a half on a 16 Mustang GT. You'll have plenty of volunteers to race you.