Odd Serial on 1941 Ford truck?

[rabidscott]

I found the frame and tranny serials on my big truck project and I'm a bit perplexed.

The frame stamp is 99I-31xxxx. It's possible the I is a T because the top slash is a bit wider than the bottom.

The tranny serial BB18-442xxxx. I realize the tranny was likely swapped out at some point but I'd like to know what it's from.

Anyone shed some light on these stampings? Are my Google skills simply weak?

Many thanks,
Confused in California