ive just perchaced a h/o 305 with 10 to 1 flat tops, 292 cam, double hump heads, performer rpm intake, and holley 600 dbl pumper. i have it idleing at 1000 rpm. the timing is set at 6 deg advanced at idle. it wants to keep running when i shut it off. im running 93 fuel. what causes this?

Cams too big for a 305 ,idle is too high and initial timing is too retarded.

what cam do i need and when i set my timing up it detonates around 3000 rpm. ?

That's due to the total timing coming in too late.
Scott Wheaton will be along to tell you how to set it up.