There have been some dimensional changes to the profile of the "ears" at the top of the grip frame and the tapered "shelf" that surrounds the cylinder frame's "hammer well" over the years. This suggests that "same vintage" parts be mated to prevent some extra work. Fortunately you've stainless guns so no "refinishing" work will be required.
Case in point:
Early '90's stainless .45 Blackhawk being fitted with a Super Blackhawk Hunter grip frame. Note the mismatch and that it's the Cylinder Frame that needs the fitting and not the grip frame!
A bit of "elbow grease" can get 'er done, though.
The hammers have been profiled to fit the "ears" so you may need some fitting. I certainly don't want to discourage you since thousands of folks have added Super hammers to their Blackhawks. Being educated that there
may be some difficulties is always a good thing.
JMHO,
flatgate