Do you need a different catalytic converter input/output diameter?
If you want a diameter larger than 63.5 mm then just cut the catalytic converter cone in the right one to the desired diameter and if 63.5 mm diameter is too large for the Shadow then you can get the reductions available in the link below:
Universal stainless steel catalytic converter with metal insert. Compatible with diesel engines.
The catalytic converter meets the requirements of the European directive:
Manufacturer's warranty: 12 months or 50,000 km.