It allows the installation of the bellhousing to be assured of being EASILY within the .010 total runout margin. It's a solid mount, and doesn't have any elbows or other "flex" that could cause the measurement to be off.
Stick a light in the bellhousing, look for gaps, and adjust/install accordingly. BAM!
I already have paid for 2 Browell units, one Mopar, one Pontiac. I am not sure what I'll have to do to use my Mopar Browell alignment tool to check the runout of the scattershield I will certainly install along with the 541 cu in stroker.
I can't imagine the diameter of the bellhousing hole in a Mopar specific scattershield being a different size than a Mopar "factory" bellhousing??
