Traction Issues

I know I will about from some people, but here go's. The other night I was out with my wife and I guy challenges me in a race with a mustang, at first I say no but......Anyway he ends up pulling me by 1 car link and holds it. I have no problem with the loosing part but how does a 87 mustang running a 468 bb on 275/60/15 drag radials hook better than I do. I am running 315/60/15 drag radials, 8.75 with 3.55 gears, 002,003 springs inset 3", 50/50 shocks on rear, 90/10 up front, adjustable pinion snubber. Yet I just destroy all through first and deep into second. How do I find out what I have wrong?