1976-1979 Mustang, S70 MKIV engine, generally a very good machine!
The engine is the same (ignore the sticker) as your corvette, so in the event of any catastrophic failure of your corvette engine, it's a straight swap and still original, further to that, any issues you encounter at all with your corvette engine can be remedied with engine parts form this.
the base is not the same, however, a number of your most frequent base failures could be repaired from this, for example, the rear 'W' clips on the axle tend to sometimes break, you will find the ones on this machine fine to replace them, wheels should be fine too, and the internal components of the starter (Spring, pulley, etc)
This mower will provide most parts you would need to be worried about, and then some.
my only warning is the base of the corvette (or either) as the alloy will break from a good stone hit, etc, and this base is not the same, so to help preserve the mower, always check the lawn for debris first!
The price is more than I would usually pay, however, firstly it would appear you have already bought it, so the point is mute, further to that, I am a collector with over 70 mowers, so for me, getting dead ones for $20 from the tip is the only way to go, and I spend a lot of time working on them, considering you wanted a reliable, tidy, complete and working machine, the price is probably reasonable, you can be lucky at the tip, t this mower seems a good purchase for you to ensure the future of your corvette

P.S. In the event of an engine swap, personally, i would swap the lower halves of the crank cases, yes it is a lot of extra work, but it keeps the engine number of the corvette, on the corvette, which is a serial that will have numbers at the front that are just for corvettes. of course I understand for most this is unnecessary extra work, but the collector/mower historian in me just had to mention it!