I see from your ID that you're a UF Gator, but we won't hold that against you, lol. Well, not too much anyway.
I think there have been many such conversions (both ways actually).
The guys in fresh water lakes and rivers seem to sometimes think the heat exchangers are ballast, and the salt water guys want (and need) them.
The heat exchanger system, despite being a pretty darn interesting and effective system, was prone to overheating if one of any number of issues arose. They calcified over time, impellers naturally go out, pump interiors wear down, air gets in at various places around hoses, bits and pices of "stuff" clog up the works, t-stats act up, pressure regulator valves collect debris, exhaust hose interiors collapse, oil coolers are an obstruction on the inlet side if clogged with debris, you name it..............any one of these can cause a motor to overheat, and there are a host of other issues too.
Mike Burdette is a PE, and here is a look at his system. He used Volvo Penta heat exchangers, and from the looks of the setup, it probably performs better than the one Chris Craft designed. Note how the heat exchanger and surge tank are built together as a unit, pretty clever. Not sure if this is an adaptation Mike did himself, or whether he found some nice exchangers that were already built like this. Note the need for a pressure cap, and different thermostat between the STANDARD systems and CLOSED systems, the CLOSED systems run hotter by design.
http://www.network54.com/Forum/424840/message/1121461323/
As far as I know, there are no kits, however, we do have highly detailed diagrams and complete parts catalogs, so you could easily build up your own kit.
Regards, Paul Pletcher (finally back from Chicago !!)