Oh yeah, that thing. I forgot all about those. From what I recall that bracket was the culprit for vibrating stock MAFs to death back in the days before translators. It was found that the MAFs live longer when they're supported by the cold air kit instead of being coupled to the engine basically turned into a tuning fork.
To answer your original question, I would guess the bolts would be a metric thread since the stock MAFs aren't original to the 3.8 design, but I would caution against mounting it to anything that will transmit NVH into the unit. They're fragile enough as it is.