Tires

    You are going to want to use bar tread tires for pulling.  They bite into the ground the best.  The most popular size to pull with is 26X12.00X12.  This means the tire is 26 inches tall, 12 inches wide and fits on a 12 in rim.  Another popular size is 23X10.50X12.  If you are running the 26's you are going to either mak your own rim for the tire or buy an aftermarket rim for pulling.  This is because the tire is too wide for the factory rims.  If you run this tire on the factory rims the tire will be crowned meaning the middle of the tread will be the only thing contacting the ground.  Run about 3 psi of air pressure in the tires.  If you are running 23's you may need a little more air so the rim doesn't spin inside the tire.
    You may want to cut the tread of your tires.  Check your rules firts to make sure you can.  Cutting means you take a grinding wheel for tires to the bars of the tires and give them an edge.  This makes them bite into the ground harder.  Take the grinding wheel and angle all of them back and take some off the front of the lug so it has a "sharp" edge.  The tire should look simmilar to the one below when you are finished.

Weight brackets, wheelie bars, and hitches

    Once you have everything stripped off your tractor you don't need its time to build a hitch and weight brackets for it. I highly recommend you do not weld anything to the tractor itself!!  Make all your brackets and hitch bolt on or pin on.  These old tractors have plenty of places to bolt stuff to. 
    Your hitch should be adjustable.  This is so you can adjust the height of it.  This is necessary because different places have different rules about ho high your hitch can be.  When it comes time to pull you want it adjusted as high as the rules allow to get a better pull.  The simplest way to build an adjustable hitch is to use a piece of threaded rod, 1/2inch plate, and nuts for the the threaded rod.  First your going to have to make up a bracket on the back of the tractor that the threaded rod can rest in and turn in.  Cut the threaded rod to the proper length for your bracket.  Use a torch to cut the 1/2 in plate to the proper size.  Cut a large hole in the plate for the hook on the sled and a hole just big enough to get the threaded rod through.  Slip the threaded rod through the bracket on your tractor through the bottom first and weld a nut on the bottom of the rod.  Thread another nut about half way down the rod and then slip the plate you cut onto the rod and let it rest on the nut and weld the plate to the nut.  Now slip the top of the threaded rod through the top of your bracket thread a nut on to it to hold the rod loosely in place and weld the nut to the rod.  Now you have an adjustable hitch.
    You need weight brackets in 3 different locations on the tractor, the back in the middle and all the way in the front.  I cant explain how to make weight brackets for tractors because of all the different designs out there and the type of weights you can use.  You will need to figure out the fabrication on your own.  You will also need to check your rules to find out how far off the tractor you can have weight.  You can use almost anything for weights.  I have seen people use old weights from a gym, cinder blocks, thick pieces of steel, cast iron, and weights for farm tractors.  Make your front bracket adjustable in and out so you can get your front weight out farther to help keep the front end of the tractor down.

    I would recommend incorporating your wheelie bar into your rear weight bracket.  Check with your rules to get the proper height and length for your wheelie bar.  Make sure you build a whellie bar strong enough you don't want it to break and have the tractor flip!!

Getting started

      Garden tractor pulling is a simple and fun sport to get involved with.  You meet alot og great people and it doesn't cost much.  Im going to tell you how to build a competive pulling tractor at a low cost.
To get started you need a garden tractor.  Look for tractors from made from the early 60's to the early 80's.  These were built to last unlike the crap you buy today and alot of parts are still avalable today.  In my opion it doesn't matter what brand of tractor you use, but it depends on who you ask.  Most people reccomend running Internation Cub Cadets.  Other good brands are Wheel Horse, Sears, Jacobsen, Gravely, and Bolens.  Alot of people will tell you to run with cub cadets because of all the performance parts that are available for them.  But on the other hand I have a montgomery ward tractor I payed $25 for and it has out pulled cubs with a lot of money put into them.
     Once you have a tractor it is time to start making it a puller.  This sounds ridulous but you need to make this tractor as light as possible.  This is so when it comes time to put weights on you can get the weight distrubuted where you want it.  This means remove everything you don't need.  This includes lights, any sheet metal not needed, the PTO lift handle, any brakets and pulleys for the PTO, and anything you can think of.  My montgomery ward doesnt even have a starter, I use a rope and pull start the engine, This got rid of the heavy starter/generator, battery, voltage regulator, and most of the wiring.  Check with the rules of the place you are pulling at and see if you need any of the belt guards in place if not toss them.  If you do need them trim them down every little bit adds up