Looking for replacement engine for simplicity 2690783 the con rod has gone in mine or do other simplicity engines fit this model any help would be great 

Is your engine:
 

ENGINE, 19.5HP B&S Intek Single (Model # 441777 Type # 0128 Trim # B1)
 
or
 
ENGINE, 22HP B&S Intek Twin (Model # 31P677 Type # 0116 Trim # B1)
 
 
https://www.manualslib.com/manual/153479/Simplicity-Regent-2690783.html
 
 
 
 
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hi there Scott its the 22hp Model # 31P677 

Your engine: 
 
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/briggs-stratton/briggs-stratton-engine/200000-399999-series/31p600-to-31p699/31p677-0144-b1 
 
That engine is of course made by Briggs, not Simplicity.
 
It's also VERY COMMON and many, many manufactured. 
 
IE, here's a brand new one that should fit (but check your engine against this one):
https://www.northerntool.com/products/briggs-stratton-intek-vertical-ohv-engine-with-electric-start-540cc-1in-x-3-5-32in-shaft-model-33s877-0019-g1-44651 
 
I put one of these engines on a customers mower.  Very easy install and all wiring was plug and play for that machine. 
 
 
 
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