The intakes for the 400/430/455 we have on record are in the reference section under Buick Engine Identification.
Here: https://www.teambuick.com/reference/..._big_block.php
B12480203 does not show. Letter prefixes are not recorded, nor are suffixs (probably why yours show 8 numbers instead of 7). There is a 1243020 which is very close and if you misread the 3 for an 8 would match.
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