Being a 03 using a 545RFE it is a electronic controlled transmission. It is currently in limp mode. It won't every work unless you can duplicate the sensor inputs and then it would by my guess not work as it should. My recommendation is to use a A518/46RH trans. You can do like I have done and use pressure switches to control the O/D and converter lockup. You will have to install a Throttle Valve cable to mange it's normal shifting which is no problem since you have a carburetor to connect to. And it is basically a bolt in with a modified flexplate and possible a different starter motor and using the original cross member with the mount holes elongated about 1/2". The driveshaft fits without any mods. Plus it is a more robust trans. Good luck.