Cam timing

Have a slant six that i'm using for bracket racing, nothing fast best it's gone so far is 15.02 but i know the cam timing is retarded. Need advice on what to run it at. Here's the cam specs:

Lift 470/489
Adv Duration 262/268
Duration @ .050 224/230
Seperation 108
Centerline 106

My cam builder said not to run no more than 104, i've read that when racing to run these engines anywhere from 98-102. This engine does not have alot of compression probably just 8.5-1, running a 3600-3800 stall converter & 4.86 gears.