FLC OF A B737-200; NOTICED ENRTE THAT THE ACFT PERFORMANCE BOOK HAD NOT BEEN CHANGED TO REFLECT A NEWLY INSTALLED DIFFERENT MODEL ENG ON 1 SIDE THAN THE STANDARD (-15 IN LIEU OF A -9). THEREFORE; THEY HAD ONLY -9 DATA TO USE IN OPERATING BOTH ENGS. HOWEVER; IT IS NOTED THAT IN THIS INSTANCE; SAFETY WAS NOT COMPROMISED SINCE LESS PWR WAS USED OUT OF THE -15 ENG THAN IT WAS CAPABLE OF PRODUCING.

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LANDED AT HUB; HAD AN ACFT SWAP. FLT RELEASE SHOWED MIXED ENGS OF -9 AND -15. ARRIVED AT ACFT; SAW NO 'STICKERS/PLACARDS' FOR AFFECTED COMPONENTS. CALLED MAINT CTL; FOUND ENG HAD BEEN CHANGED LAST NIGHT (NOW BOTH - 15'S). CALLED DISPATCH; REQUIRING NEW RELEASE. WENT TO GET NEW PAPERWORK. ABOUT THIS TIME; FO NOTED 3000+ LBS OF FUEL IN CTR TANK. (WE NEED FULL WINGS IF CTR GREATER THAN 1000 LBS). HE CONTACTS MAINT TO START MOVING CTR TANK FUEL TO MAINS -- WHICH (OF COURSE) NOW REQUIRES A NEW RELEASE BECAUSE OF 3000+ LBS FUEL. FINALLY ENRTE; FO AND I BEGAN DISCUSSING ALL THE CONFUSION. THAT'S WHEN WE DISCOVERED THE 'PERFORMANCE BOOK' HADN'T BEEN CHANGED (STILL HAD -9 ENG DATA). SAFETY NOT (NECESSARILY) COMPROMISED BECAUSE WE HAD DATA FOR THE 'LOWER' PWRED ENGS. SO WE WERE OBVIOUSLY (IN THIS CASE) OVER PWRED BY OUR CALCULATIONS. BUT THERE WAS TOO MANY THINGS GOING ON TO CATCH 'EM ALL. WE; THE PLTS; AS THE ULTIMATE SAFETY CATCH; NEED HELP FROM OUR COMPANY; TO HELP INSURE ALL PROCEDURAL ASPECTS ARE IN PLACE -- TO HELP US WITH THE SAFETY OF OUR PAX. CONTRIBUTING FACTORS: 1) ACFT SWAP. 2) NEW COMPANY PROC FOR ACFT LOG BOOK THAT DOESN'T LEAVE MUCH INFO IN BOOK (IE; NEW ENG; NOT SHOWN IN ACFT LOGBOOK). 3) SOME PARTS DONE; IE 'STICKERS REMOVED;' OUR 'SPD BOOK' CHANGED. 4) FUEL IN CTR TANK -- NOT JUST 3000 LBS EXTRA. 5) OUR SCHEDULES -- WE ARE REQUIRED TO FLY FAR TOO MUCH. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE COMPANY HAS SINCE HAD A MEETING REGARDING THIS DISCREPANCY ALONG WITH OTHER ISSUES TO ATTEMPT AVOIDING A FUTURE RECURRENCE. HE STATED THAT THIS ERROR WAS DIRECTLY CAUSED BY A LACK OF COMPANY COM BTWN MAINT AND OPS. IT WAS THE RESPONSIBILITY OF MAINT TO PROVIDE APPROPRIATE OPERATING DATA AND PLACARDS FOR EQUIP CHANGES. HE FURTHER STATED THAT ONLY TIME WILL TELL IF THIS SAME PROB HAS BEEN CORRECTED. THE LOCATION OF THIS INCIDENT WAS PHOENIX; AZ.