So I went to the old bolt bucket and found a Pontiac cylinder head bolt with the stud that the negative battery cable mounts to. It was the perfect stand to mount the modified bracket to. Thankfully 455 blocks are predrilled for four bolt mains and the bolt just screwed right in. (along with some red Loctite to keep it in place).
And after two hours of test fitting, drilling, heating, bending, reheating, and rebending, the bracket mounted up nice and tight in the correct position. I used red Loctite on the nut as well as centerpunching the edges of the nut to crimp the threads slightly. I test fit the oil pan with the dipstick tubes in place, as well as spun the crank to make sure it was a long way away from the reciprocating assembly zone.
