Yes, the COM will bolt to the Y bellhousing. The FOM converter will work only if the FOM has a 29 spline input shaft, not the smaller 17 spline one.
The FOM is an early 56,air-cooled,so it's probably going to have the smaller spline.If so,can I use the COM convertor and flywheel?Or is this like the FMX swap and require the front pump and input shaft to be swapped.
The FE flywheel will not bolt to the Y. Also, the snout diameter on the FE converter is larger than the Y. Your easiest way would be to find an air cooled Y converter with the 29 spline turbine or a '59 and later Y flywheel and converter.