The 346 heads (71-73) were induction (flame) hardened seats whereas the 452's were stellite material (solid hardened metal, not just surface hardened). There were a couple of other part number heads from 74 to 76 that had insignificant changes as far as guide thickness, etc; but all ports were the same from 71 on, so one is as good as another.
The probability of any 71+ versions seats having ever been replaced is nearly non existent unless a machine shop was just making a project out of a set just for the business. They are some tough seats, and even if a valve was bent, or some other catastrophe damaged a seat, just that seat would be replaced.
No BB head had a non-removable seat unless there is some weird industrial head I have never seen, and you can't really tell by looking if it's a stock seat, or replacement, unless it's a huge aftermarket seat like the ones that are pictured above (most replacement seats are not nearly that big a diameter).
Your 440 should have 346 heads on it and unless the valves or guides have abnormal wear, you can probably just lap the valves and be good as new.
I am not sure about your experience with Mopar cylinder heads, but this post is so full of inaccuracies and misinformation, it is hard to find a place to start. Induction and flame hardening are two seperate processes, not the same. The 452's did NOT have stellite seats from the factory, although they very likely had Stellite faced exhaust valves, and replacement seats can also be Stellite. I have replaced plenty of exhaust seats on late model heads. Once they have had a valvejob or two, the thickness of the seat is inconsistant. I do not replace seats so I can make a project out of it, but instead, the job is necessary. If you have a head, or set of heads off, and need to replace a seat, NOW is the best time to do the rest. They have all gone the same distance, and it is cheaper to do it at that time instead of the second time. Most customers want all of the seats replaced anyway, unless they do not have the money.
I do not understand this comment "No BB head had a non-removable seat unless there is some weird industrial head I have never seen, and you can't really tell by looking if it's a stock seat, or replacement, unless it's a huge aftermarket seat like the ones that are pictured above (most replacement seats are not nearly that big a diameter)." No cast Iron head that I have seen has ever come from the factory with a replaceable seat, and these seats are nowhere close to being "Huge". These are stock size replacement seats on both sets of heads.
Virgin heads from the early 70's are 40+ years old, and WILL need guides, 3 angle valve job, surfacing, new valves, springs, and quite possibly, exhaust seats. Heads that have been gone thru a few times will need everything with the exception of guides, depending on their condition. I would NEVER just recommend just "lapping" the valves as this is not 1955 anymore. If you have gone thru the trouble of removing everything to get the heads off, and you don't do a valve job, you are just asking for trouble.
