While some custom fabrication shops *might* be able to create such an adapter plate, it would be a significant undertaking and very expensive. You'd be essentially commissioning a one-off piece of engineering. The complexity arises from:
* Different bellhousing bolt patterns: The Cummins and the TH350/TH400 have completely different bolt patterns. The adapter would need to bridge this gap.
* Pilot bearing/input shaft diameter mismatch: The input shaft of the transmission needs to correctly align with the pilot bearing or bushing in the crankshaft. This likely requires custom machining.
* Torque converter considerations: The torque converter used needs to be compatible with both the Cummins output shaft and the TH350/TH400 input shaft, which is another area requiring custom work or finding a very rare converter.
* Alignment: Precise alignment is crucial to avoid vibration and premature wear.
In short, while theoretically possible, creating such an adapter is a complex project requiring advanced machining skills and specialized knowledge. It's far more practical and cost-effective to choose a transmission that already has readily available adapter plates for your Cummins engine. A more common and easier solution would be to find a transmission (like a suitable Allison automatic) that already has a readily available adapter for your Cummins engine.
