That fracture looks like a “fatigue crack” that started at a “stress concentration edge” that the original part designers never should allowed to stay in the final design.

The “improved part” from the ebay ad does look superior.

If you absolutely had to repair that - braze it - not weld it or JB Weld Epoxy.
Prior to brazing add steel stiffeners above and below as clearance allows.

Instead of throwing the broken part away,
package it up and mail it to:

Department of Mechanical Engineering
Duke University
Durham NC
attn: Failure Analysis Class

Add a short note saying that you suggest
a 4th year engineering student take on what caused this part to fail for their end of class project,
and that many hundreds of these parts are/were in service around the USA.
( Students are always looking for a worthwhile failure to investigate)

Both CAT and Cummins hire 2-3 Duke students per year,
although the majority of Duke mechanical engineering students are Navy ROTC
(and us taxpayers pay their +$75,000 year tuition)

How many hours/miles on that 3406E ?

In the 1980s it was the repeated failures of $27,000 CAT turbochargers on 992 front end loaders that gave me heartburn.
$27K back then would be $90K today.

Years later when reading WW-II history I learned that turbochargers were a huge headache on aviation engines.