ARMA rules
http://www.golawnmowerracing.com/mod...download&cid=1 ULSMRA rules
http://www.letsmow.com/rulebook.asp The frame you want will depend on the class you plan on running, if you are going to build it to a sanctioned group. They have wheelbase and configuration requirements that vary from class to class.
Many transaxles don't need the spiders welded to lock them, just add 2 more gears to the differential. No need to weld it and it's removable. You should consider just running a tranny/live axle setup instead of a transaxle. More gearing options, easy brake mounting, no need for a jackshaft when lowering.
Take a while and read over some of the sections at
http://www.heymow.com you will learn quite a bit.
