The pumps are a bolt-on interchange, bolt to the front of the transmission case with 4 bolts with a square section O ring for a seal.  Only caveat is the front input shaft.  If your original trans and converter have the smaller 17 spline input shaft (sticks out the front of the pump), then the converter will not work on the 29 spline FMX input shaft.  You will have to tear both transmissions down so that you can put the FOM input shaft in the FMX.  Another way would be to find an early converter with 29 splines, they came in both configurations.