So I've read the only diffrence is the mounts are a little diffrent, does anyone know what exactly needs to be dont to make the s5 tranny bolt into the s4? Fabricating a new bracket or is their an easier way?

I suggest getting a used S5 crossmember from a junkyard or somewhere and buying the 3 new bushings from Mazda. With the crossmember you will also need the plate that mounts to the transmission.

You can buy all the parts directly from Mazda, but you will save money getting the steel parts used if you can find them.

You could make a custom setup but that would not be easy, as the system is somewhat complicated and if your new mount is too rigid it will transmit a crapload of vibration and noise into the car