Rochester Quadrajet ID issue

[czarcaustic]

Hey guys ... my carb is spewing gas all over the place so I have decided to rebuild the ol' quadrajet.

I grabbed the stamp and then went online to ID my specific carb but something has confused me.

Stamp says:

7046216 YD

I understand:

70= Rochester
46= ???
2= 49 state emission
1= chevy
6= auto tranny
YD= ??

The questions:

Everywhere I check 46 is not an option, it SHOULD stand for 1976, however this engine (and I assume carb) is off of a 1980 chevy pickup (PO swapped the ol inline 6 for the 350/350). Furthermore it seems that rochester went to the 170 prefix in '76 and I don't have a 170 prefix. Is this something anyone else has run into?

What is the YD?

Any help from the all knowing would be greatly appreciated!

Czar Out!