I was the welder /fabricator for Van at Elite karts. The biggest difference between an Elite III sprint and a sit up enduro sprint, is the wheelbase as mentioned at the beginning of the thread. It is somewhere around 2 ” longer. Depending on the build date, there may be some subtle differences in tubing thickness and gusset placement. The front end geometry and chassis layout is the same as an Elite III Sprint. Bolt on parts such as wheel offset, Front wheel brake spindles, axle length, motor mount offset, seat and body work are the differences. Try it the way it is as others have suggested. The chassis number is under the master cylinder. Was your father the original owner?