833 OD bell housing dust cover (s)

Yes, you need both. The flat one could be cut out of sheet steel (your neighbors sign) and goes on the front face of the bell. The other one covers the lower portion and likely adds some strength when it covers the gaping hole in the bottom of the bell.

There are different sizes of at least the lower one depending on the bell vintage and clutch size, I suspect the same for the forward one and it probably is different bb to sb.

Brewers has them both and has both new and used of the lowers for a reasonable price. They also have good descriptions of the sizes and p/n's.