Some of those engines had problems with fuel pooling between the carb and the crankcase. They would run OK but when tipped or turned suddenly after a period of idle, they might just die for no apparent reason as the fuel dislodged and flooded the engine. This is the main reason the engine was changed to a rear intake configuration. Add to that these were engines produced early in DLE's history and the quality control wasn't always the best. There were a number of quality control and material issues that were resolved in the years following those early engines.

You can still buy the rear intake conversion kit and if not easily found, the individual parts are quite reasonable. I'd probably just run the engine as is to see how it works out.