Very cool indeed. Very early crossover pipe before the toaster was added? It is quite similar to the crossover pipe I've seen on the early prototype 'mules' in magazine and in person at the CMEP in Columbus, IN. But they didn't have the cast CTD insignia.
Bill Gilbert 85 D350 crew with 90 6BT intercooled Getrag 3.07's 93 D350 single cab Getrag 3.54's.
Probably a stock Cummins part off of a who-knows-what application.
If you have the part number, you can probably find a warehouse they have of them.
1990 D-250 Regular Cab: Tweaked injection pump, built transmission, a cataclysmic charlie foxtrot of electronics, the most intense street-ran water injection system in the country, and some more unique stuff.