383 intake manifold change AFR big time

I’ve never done that particular swap, but I really wouldn’t expect there to be much of a jet change requirement.

On the dyno, my 383 didn’t require any jet changes going from the factory intake to an RPM.
And multiple carbs were tested with both intakes.

I’d be looking at a possible float height or fuel pressure problem.
Try a new fuel filter, make sure the timing is correct.

Maybe see if you can borrow a different carb for testing.

Another thought, is it possible the added height is causing an issue with the air filter and/or air intake into the motor?