Ty is right of course, regarding the engine's size and date of manufacture (it's actually 465.7 cc - the 28 cubic inch figure is rounded from 28.42). It is a second generation design, with a vertical crankshaft and flo-jet carburetor, plain main bearings, and an electric starter (12 volt gear drive, with alternator). The operator's manual is here:

http://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=mssAIQ-K_ny7tH217FzoPu

The illustrated parts list is here:

http://bsintek.basco.com/BriggsDocumentDisplay/default.aspx?filename=Z6ntzHVJ1DajI

You can find the universal B&S overhaul manual for engines of that period here:

http://www.tpub.com/content/recoveryvehicles/TM-5-4240-501-14P/css/TM-5-4240-501-14P_70.htm

(Use the "next" button to leaf through the 225 pages.)

Can't help you with the mower manual, but as Ty said, you could begin with the parts and manuals section of this site - there are quite a few manuals for Victa ride-ons there.