What is wrong with the engine exactly?
Briggs oem parts is the best way to go,
Parts lookup and repair parts diagrams for outdoor equipment like Toro mowers, Cub Cadet tractors, Husqvarna chainsaws, Echo trimmers, Briggs engines, etc.
www.partstree.com
and a good repair manual, briggs 270962 manual should be for this one i think.
the wise thing to do is to tear it all down, and (if you have the know how) or have a machinist, measure the cylinder bore and see how bad it is worn, if it would need bored out, or just a new ring set. of course regardless, new oil seals, correct thickness crankcase gasket, valve job, checking tolerances on the crank rod journal and other bearing surface clearances. probably several other things im leaving out.