I'd heard 100 in the past too, but I don't believe it anymore. It may be 100 from a particular assembly plant.
My best guess is the original build for sale in early 1974 was only 100, and this is why we only see them in particular driveline combinations and trim. After that initial build were sold (let's say by May 1974) you could order them how you wanted and this may explain the few rarer trims (like 38J) and autos that exist later. You'd have to have been quick though as any orders after the start of July would probably ended up being HJ.
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