[GMCPaul]

Thanks, the stainless steel screws are already in production and will be here in a week or two. We appreciate the help. In regards to screw head diameter it's actually supposed to be .50" according to GM master parts catalog, the slight deviation you you are seeing with the micrometer is the fact they have a plus or minus tolerance in manufacturing of hardware.
Thanks again!!
Paul Jr @ GMCPauls