The 737 and 757 (and 707 and 727) all have exactly the same fuselage diameter, the 757 is merely longer. Seat pitch is determined by the airline. I agree with

The 737 and 757 (and 707 and 727) all have exactly the same fuselage diameter, the 757 is merely longer. Seat pitch is determined by the airline. I agree with you about the re-engining though. Seems Boeing might have pushed the 737 airframe one generation too far.