I have the L297 IC all set up but I have a Bipolar Stepper motor and not a UniPolar stepper motor like in the first picture on the site.
I only bought NPN transistors and I wouldnt want to build another H-Bridge since that will just void the whole reason for the L297 IC.
I dont see how the Diodes would supply 12V to the motor in the current schematic and I also dont know how I would reArrange the circuit so that it will supply 12V to the motor but also inverts the supply when it is its turn to invert?
You can design your own circuit and drive the coils according to their step requirements by the help of any micro controller and 2 nos of full bridge driver (8 nos of transistors.) or you can use a dedicate IC for this purpose like LDM18245.