Xtreme Mower Mayhem

i wanting to make a 4x6 lawn mower but dont where i could get a step pulley and kind try to figure out the pulley size on each tx want to put 4in on both but not sure if that will work so i need some ideas

What about welding a sproket under the first trans's pully that runs to the another sproket on the 2nd trans and link them with chain?  That way they would turn at the same rate....like a timing chain.