I am an 11B who has completed his reclass packet for 35L (old 97B) My ETS date is this AUG and my DEROS date is March 09. I filled a 4187 (reclass)and stipulated that I would reenlist to meet the reclass requirement if accepted. So if I reenlist 11B and take a bonus will I have to pay it back even though the multiplier for 35L is the same? If so can I extend then reenlist after I am award the MOS? Any other Ideas?

No, you cannot reenlist for your current MOS and then switch to another. You'd be paying the bonus back.

AR 601-280, Army Retention Program, Chapter 5 (Bonuses), paragraph 5-6:

i. The following restrictions exist. Regardless of whether a Soldier is eligible under paragraphs e, f, or g above, a Soldier is ineligible for a SRB if the reenlistee—
(1) Is entitled to readjustment, separation, or severance pay.
(2) Reenlists or extends to gain enough obligated service to take part in a program leading to commissioned or warrant officer status.
(3) Enlists in the Regular Army following a discharge from a Reserve Component during or at completion of ADT, AGR, TTAD, or ADSW (Active duty for Special Work) tours.
(4) Has been officially informed that the Soldier’s application has been approved for attendance at an MOS-producing service school or course and that successful completion will result in redesignation of their PMOS. This does not apply if the new PMOS is in the normal line of progression of the PMOS held at discharge.
(5) Selects an option for retraining, and the successful completion of retraining will result in a change in the Soldier’s 3-character PMOS. This restriction does not apply if the new PMOS is in the normal line of progression of the PMOS held at discharge.