BowTieEater - I believe the reason they didn't call it a 4.9L instead of a 5.0L is because then people would get it confused with the straight six truck engine. They had the 4.9L, 5.0L, 5.8L, and 7.5?L (460) in the trucks for quite some time and by the time they converted engine sizes from cubic inches to metric Liters there were two very different engines with similar displacement. Plus the "5.0L" was designed to be upscale from the 4.9L so by making the engine size "larger" and designing it with more power than the 300-6 it became a more expensive/"better" option. I believe the 300 straight six started off as a 240ci engine in the sixties, but i'm not sure when they increased the stroke to make it a 300....anyways, At least this is what i THINK they had in mind.
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previous name: 84stangLX
'84 Mustang 5.0 LX
my LX
'89 Mustang GT
my GT