500cc OHV Gas Engine for my old John Deere lawn tractor

I am considering a Briggs 500cc OHV Gas Engine to replace the Kohler Commander that sits on my 1995 John Deere STX38 lawn tractor. Any comments, suggestions, ridicule?

Guess this is YOUR machine ??

http://www.tractordata.com/lawn-tractors/000/0/9/96-john-deere-stx38-engine.html

Changing engines from one brand to another, is done often, although sometimes a few issues come into play...

engine mounting,..... sometimes re-drilling new mount holes, (including hole for crankshaft)
pulleys..... sizing the pulley on the crank, ( may involve PTO issues , electric-PTO, engage-lever )
belts ..... Drive and maybe transaxle
throttle and choke linkages.... new/ re-route
wire harness..... I SUGGEST... you have wiring diagrams of old & RE-placement engines, usually found in your MODELS part's and/or shop SERVICE manuals, sometimes, this can be a can of worms, or easy as a few wire splices ( correctly done ) changing wire colors
fuel tank... sometimes need to be adjusted or moved
oil-drain port & filter ..... EZ access
exhaust... muffler issues
will body panels fit over replacement engine / modify
will there be any maintenance obstacles

in any case.. I would try my best to have the related manuals for the MOWER & ENGINES handy, and I also suggest you take TONS of pics of EVERYTHING, and of each step you do, these engine swaps are NOT covered in the manual, the pics become YOUR manual, and will save many headaches ....... ( especially spring connection points and location of brackets )

just some of MY thoughts.... I wish you well and you can always visit here for help, ..... Boobala

more info. ............... https://www.youtube.com/watch?v=litTZViYbkI