Don't know what you need. Did learn that most mowers have the deck stamped for a 10" bolt circle which fits single and V twins. Last year I bought an 18 and 20 hp BS V twins off ebay for about $600 with free shipping, both new factory overruns....surplus engines after production like for a type mower was closed down type thing. One replaced a 17.5 single on my JD L110 (the L 120 is the same machine with a V twin anyway), and the other replacing a Kohler Courage single on a Husqvarna 46. Both drop ins on mounting dimensions. Electrical connectors matched pin for pin and location, fuel line matched but since the throttle on the single is on the left side and on the V twins it'd in front I needed to get longer cables. Bought the JD dual controlsoff ebay for 25 bucks each which were super controls....mounted to the left side plastic cowling. Love the conversions.
I noticed Northern tool is advertising BS twins at about that price too.