Small Engines (Lawn Mowers, etc.): B&S engine swap, briggs and stratton, shaft diameter

Question
I recently got a small riding mower from a friend for free with a seized up B&S 12HP model 282707 type 0122-01 code 960315ZA engine. The mower is in great shape otherwise. I have looked around online for a replacement engine and have come to the assumption that this is no longer availible. I see other engines that look to be the same but have 13.5 HP ratings. My question is, are the bolt patterns to mount the engine to the frame of the tractors the same? There are so many model numbers that I don't know the difference. If possible could you direct me to the B&S engine I could use? I know the shaft size is 1"x3 5/32". I see a bunch of engines with this shaft size in the same HP ratings (12-13.5) but don't understand why so many different part numbers.

Answer
Hello Eric:

The Model Numbers Designate the Application of the Engine, some External Components and Other Internal Component Specifications. Using the Proper Model Numbers is Required for Only Some Components of the Engine. If you have Located an Engine that has the Same Shaft Diameter and Length and Uses the Same Crankshaft Key Way, then Usually the Mounting Bolt Pattern will be the Same. There is a Briggs and Stratton Catalog that May Assist you also. the Site Addy is: http://faqs.custhelp.com/cgi-bin/faqs.cfg/php/enduser/std_adp.php?p_faqid=1487 and Click on the Blue "Replacement Engine Catalog" Words to Download the Catalog. If you Hit a Snag or this Does Not Correct the Problem,  I am Here if You Require More Assistance. Hope this Helps. Let me Know What Happens, Please. May the All Mighty Bless You and Yours. Thanks.

Good Luck

Respectfully

John

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Respectfully

John