ARP main stud interface with oil pump

yeah - tech line 101: "really? We've never heard of that...".
For 20 years now I've just cut the stud down, use the 12 point nut, and you may need to grind the chamfer off the end of the nut. Some I've had to, some I haven't. I also always run an oil pump gasket - I know some here don't and that will effect what you have to do too.