Airhorn,
Welcome to the forum.
If you go to "Other AATVs" and do a search for "Skipper", you will find some threads about your machine. The engine selection would depend on whether you plan to use it as a trail machine or racer. Generally, if you use it as a trail machine you would select a 4 stroke V-Twin engine like a Briggs & Stratton or Predator (inexpensive Harbor Freight brand). If you are into racing, a two stroke might be your choice.
I am not familiar with the Skipper, but there may be some members that could help you more. You may want to look at changing it over to a T-20 transmission since that is a very popular unit and parts are readily available for repairs and rebuilding.
http://www.6x6world.com/forums/searc...archid=6872645
Borrowing tools is for the weak.
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2000 Max IV, 25hp Kohler Command, 26" Titan Tru Power AT's
1996 Max IV, 18hp Briggs, 24" Serwas
1998 Max IV (project in waiting)
1995/1999 Max II, 16hp Briggs, 21" Rawhides
Hustler 950 (Project in waiting)