They're not all reverse compatible, only AM3 heatsinks that use the mounting clips work on AM4 without a special mounting. The Spire and Stealth use the mounting holes of the backplate and they have a different hole spacing from the AM3 socket so they won't work, but the Prism uses the clips.
I think you would most likely run into problems with memory and VRM heatsink height if they are extra big on your board. But I also think the standards for spacing and heights of memory and VRM components from the CPU shouldn't have changed if they are part of the ATX standard.