The intakes, due to production practices, were likely cast in large batches. We see this practice in many parts were machines were set up to make a run of mufflers, for example, for single exhaust V8 Mustangs. Then once they got their supply then machines were adjusted/changed to produce another style/type of muffler
As for the difference in early Boss 302 intakes the story is that whom ever was responsible for casting made a spelling error in the first batch with FIREING spelling. Some of these got out to the production. Once someone discovered the spelling error and the embarrassment related to that (surely other department heads ribbed the head allot) someone got into allot of trouble, the spelling was correct on the next batch. In an effort to save the ones (misspelled) in inventory someone was tasked with grinding off the misspelling and those made their way into production use.
So you have at least three versions (the Boss registry had someone cataloging the applications) the misspelled, the ground and the correctly spelled
Hope this helps explain what we understand happened
