440 what am I missing here?

I have seen many with your same thought . Believe me Put a 3500 converter in and your eye will open wide . That would be the lowest stall. Myself I would put a 4500 9" tight. Then hang the hell on.

Muscle cars came from the factory with 3500 converters 340's stalled at 2800-3000 form the factory same converter behind a 440 3000-3300 I played with factory converters for many years.
The truck is laid out easy enough that a convertor won't be that big of a job. Its happening. Thanks for the reply