[cleandan]

It depends on what your engine is exactly as compared to what "they" said would fit.
If your 392 is running uncut flat tops with zero deck and your current heads have smallish valves then yes, you will have clearance issues with the AFR's.
If you are running a street atyle comp ratio, say 9:1, with valve reliefs in the pistons to fit larger valves then you may have no fitment issues.
The real story comes from trying them on your motor, or at least one head for clearance fit trial. This IS a bit of a pain, but you will know for certain if you do a clay mold clearance test.
If you know your deck, your piston part numbers and if anything custom was done to them, your current valve size, and the lift/duration of your cam, and how it was installed (advances/retarded) you can get a very close approximation, but nothing beats clay clearance trials.