Engine ID - tried everything

Hello all, newbie here!

I am trying to ID my engine, but am having a bear of a time. I went to all the websites with all the charts, but i just cant seem to make heads or tails of this. Here is what i have

at the back (casting number) is the number 3970010 - which is a 350 (car, truck vette)
Perfect, no problem there b/c it is a 350.

Here is where it gets squirrley:

Serial Number: 99YC43301

Code Number: V0424F

the code, using the charts i found, show V = Flint, 04= April; 24= day. The problem is the "F", that equates to a 56 chevy or something like that.
Help!

the serial number is all wierd too, i cant find a "99" designation.

If anyone can help it would be greatly appreciated.

Thanks

Ron