Sometimes circumstances just erase all doubts: the engine drips oil from the stump of a connecting rod hanging out are covered with recently-molten aluminum: a sample of oil from the crankcase twinkles with tiny shards of journal and bearing metal, grit rubbing sharply between your fingers.
What a difference a year makes. In ’97 the big fear was availability of R-12 at a reasonable price, and being ready to do a retrofit to R-13a if it wasn’t.