Which GM automatic transmission do I have?

I have a spare V12 with transmission. I have no idea of the year of manufacture other than it is FI and had cats, The transmission has the number 24 cast on top of the case. Is this a TH400 or a 4gl480?
Thank you

Hi- Easiest way to identify is by transmission oil pan shape. If it’s mostly rectangular but a couple clipped corners it’s a 4L80E. If it’s vaguely shaped like Texas it’s a TH400. You can google up an oil pan picture if you need to be more exact. -John

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