OzyDuster74 chassis connector questions!!

I have not used the Bouchillon. However, I will the next time I need one. It has the holes for the 5/16 holes on a stock/ish convertor. The ATI has the holes for 7/16 bolts.
I will have a custom convertor as the motor will end up with a cam etc, so would think ill try get it with a tapped thread to make it easier to install box etc