All M113 kits I've built¹ that had an interior, also came with decals for things like the warning placards and data plates. Which kit do you have, that doesn't include them?

FWIW, I would go through my spare decals box and send you some, but as you seem to be in the USA, that would take ages.

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¹ Here's an impression:

[ATTACH=full]139933[/ATTACH]