Walt, other than the obvious embarrassment of running AC Delco plugs in a Ford engine, follow the old "if it isn't broken, don't fix it" adage. The R45 is hotter than the R43 so if it's running well now, why change? Are your plugs indicating a problem? Is the engine pinging? The Autolite 25 may be a close match heat-wise but I don't know (George?).
I would trust Julian's recommendations here as he has a lot of experience with Ford engines and Panteras.
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