I test fit the dash and found that certain areas had to be trimmed for it to fit properly - all of the trim work was done with a sharp utility knife which made things easier.
The screw holes and edges here . . .
. . . sit on here. See the plastic slot under the screw tab that the dash slides into? I had to sand the fiberglass just a hair thinner than it was to get it to slide in properly
the fiberglass that I originally had wrapped around was cut along this line so the dash will sit on the forward shelf properly
I also had to cut small notches for these clips . . .
. . . . which slide into the dash here
so now that I know the dash fits with the fiberglass on it, it gets one very thin coat of bondo to fill any pin holes or irregularities before final sanding and paint