when thinking about any mods, a good place to start is with 2 questions: how does it help? and how does it hurt?
to get you started...
in the benefits category, we know that theyre supposed to use less power, thus increasing economy and performance (by a minimal, probably unnoticeable degree). another possible benefit is that you would be able to run a much more agressive fan, sucking much more air when needed than a flex fan, thus preventing (or reducing) overheating while running AC while stopped
in the problems category, many of us have had the fan clutch assy fail to lockup as it should, thus rendering the fan inoperative. but then we have to ask ourselves if that fan clutch was the 20 or 30 year old original that only recently failed. also, it costs a certain amount of money for the parts, which is unnecessary IF your current system is good enough
i'll let you continue answering those questions according to your thoughts.
what are your goals for wanting to switch to a clutch fan? overheating problems?
note that i have seen plenty of fan clutches that bolt directly to your old-style waterpump (mounting flange for pulley and fan, as opposed to fat threaded hub to screw on clutch assy), so fitment shouldn't be a problem. and all flex fans had a spacer behind them, and i would think the thickness of the clutch assy would approximately equal that of the spacer, putting it in proper position.
at the end of the day, i see no reason why you couldn't
