The 24428 blade you first mentioned is a universal mount blade. Since the price is nearly the cost of the dozer blade, you would be better off with that setup.
According to the 2007 Sears fitup guide listed in a sticky at the top of the forum, the 24414 snow/dozer blade is the correct blade for your given model number. The 24412 that you found will not fit on your tractor. Here is the difference:
The old 24412 blade has a simpler mount and raises and lowers using the deck lift lever. The dozer lifting height and lowering depth is controlled by the deck adjustment knob. Also means that the mowing deck must be off to use this dozer blade. There is just 1 arm on the right for pivoting the blade. Since this blade design requires use of the deck lift mechanism, it can be used ONLY on these older models with the deck lifting arm on the front right side. (The newer tractors have a lifting lever on the left fender.)
The newer 24414 uses a more complex mounting. It does NOT require removing the deck although I wouldn't want it on anyway. It has 2 arms- 1 for pivoting as before and also a new one for raising and lowering. This design could probably be used on any year garden tractor since it is independent of the type of deck lift mechanism.
The blade itself, the pivot, the reversible scraper bar and the skid shoes are the same design on both.
Interesting note: The Sears website for the 24414 is actually still showing the older 24412 blade!
You will still need weights and chains (which are the same as for the 24412 setup)
Hope this helps!