If they end up getting it:
1. Do an alternator conversion if it hasnt been done already. The kits on eBay are pricey, but worth it if you cant fab up your own brackets.
2. Make sure it has the 4-inch heat exchanger, not the early 3-inch. The 3-inch exchanger simply cant keep up. Clean it with muriatic acid every other year or so. This can make a huge difference.
3. If they overheat, they blow the head gasket very easily. Use only a Mercruiser head gasket, not any old Ford 460 head gasket. A 460 head gasket intended for an iron head/iron block engine will fail in short order.
4. The later aluminum exhaust manifold was much better than the earlier cast iron units, as the cast iron ones tend to crack, allowing water into the cylinders, mainly #4.
5. The water pump is an impeller on the end of the camshaft. If its leaking you'll have to pull the front cover and various other bits off the front of the engine to replace the seals. If the cam seal surface is pitted, and it always is, either get a new cam, have the existing one sprayed and remachined, or use speedi sleeves.
6. The 4 bbl carb is similar, but not the same, as the ones used on the 4.3's, 5.0, and 5.7's. If your's needs help, rebuild it yourself, properly. If you get a new one, you'll be given the wrong one, I guarantee it.
Thats my advice after 15 years of ownership. The Breezeworks 470 forum has a wealth of knowledge, but its not a terribly active forum anymore, at least when I was there last (a couple years). If the engine was well maintained and doesnt have any huge problems (water in cylinders, cracked manifold or riser, etc) then it can be a decent engine. Very powerful for its size, and easy on gas. If it was neglected, severly overheated, sitting unused for years on end, or is one of the very early models, I'd look for some other form of entertainment, it will nickle and dime your sanity to death.