Both the 392 heads and the early K heads (even a K0 one I have) have ~33.9mm intakes (OD on the non barb portion) and the ID is about the same. So basically any and all K heads have the same inlets on the head. Both K and F carbs also have the same diameter for the PD's (in the inlet), which is different than the round-tops.
There are three manifolds available, one for all the older K's, one the later ones with PD's and one for the F's.
This means with the early K rubbers + early K head you can fit roundtops, late K rubbers + early K head you can fit PD's, late K rubbers + late K head you can fit PD's, and early K rubbers + late K head you can fit roundtops. The jetting is probably close enough on all of them that you can tweak it to make it work (I've done it for both on a freeflow 4-1 setup with a K&N in stock airbox).
As for the difference in PD carb jetting, you can easily get away with a jet kit or OEM jets to account for that.
The rationale for running round tops is that they're super easy to clean and look mechanically awesome. You can also delete the cable choke and they polish up nicely (and can be bored with some $$$ or skill if janky and looking for power).
The rationale for running round tops is that they don't have the flat spot off idle, actually have a really nice tuning system, and since everything is all internal, I often find they're in much nicer shaft on the linkages/etc... The idle up cam is also cool.
I wouldn't go out of my way to run one or the other, but considering that you end up replacing most of this stuff when doing a resto or build...it's not out of the question to be swapping.
