I may need to be going with the 450 3-1/4 if I want to keep the forend with the gun and keep the original barrel contour which is nice.
I think that for the No.2 or 470, the channel would need to be opened up and the forend doesn't look like it would take it.
Another option is to go for a full boat resto with new wood and everything but I don't know if I can stomach that right now.
It is a neat action though and more stout than any other I have had or held