Well kinda sorta, you didn't specify New/Old model but my answer is " kinda sorta"
They can but you have to chop, cut, re-build.
The Old Model is easiest, Chop off the top, I have seen this before, it's ok, but that's a $125-150 hammer you're chopping.
I'm currently doing a OM build where the thumb was cut off the Single Six and NM Super were swapped, welded, re-shaped.
Here is a picture showing OM hammers, Hawkeye to Bearcat.
Hawkeye, Super Blackhawk, LG Blackhawk, Med Blackhawk, Single Six, Super Single Six, Bearcat.
Photo credits:weaselmeatgravy
NM can be chopped, but you would have to address the transfer bar ledges, or again graft the tops.