You're confused/misled.
DT466 is an engine built by Navistar/International. It's a member of the DT family which includes the more rarely found dt360,dt408, and dt530. The number after the DT indicates the engine displacement in cubic inches.
Cummins makes the B and C series engines(along with others, but these are found in busses). The B series is 5.9 L in displacement while the C is 8.3 L.
All three engines will work. The dt466 went to electronic control and HEUI injectors in the mid 90's. While Cummins went to electronics in the late 90's.
If I had to choose, I'd choose the dt466 because I feel it's a stouter, more serviceable engine. But I wouldn't shy away from any of them.
The most important factor in choosing which engine is how well it was serviced. Poor maintenance can ruin a good engine. So let the maintenance records and mileage be the deciding factor.