The information is available in the B 737 Flight Ops Manual IIon performance or what is now known as the Flight Planning and Performance Manual. The Field Length limited Weight minus the Climb/ Obsacle limit weght is approximately 50% of the improved climb weight that can be added to the Climb limit weight subject to limitations. Please refer Boieng FLIGHT PLANNING AND PERFORMANCE MANUAL . The ADV version may have JT 8D- 9A or -15 OR -17/17A Engines so you will need to refer to the one applicable to you. For the JT8D-17A, the improved climb is covered in pages 1.2.4 to 1.2.10. Also the rEduced Take Off thrust is covered in the QRH Performance Inflight - General PI.20.9 . I hope that was useful ?
