Grogant: If this carb is OE than it should be a #4180 Holley. No big problem on rebuild EXCEPT there are no idle mix screw showing.They were preset at factory and have a thin casting over top. The most important thing is to replace ALL three gasket under carb..I found them to only be available from ford .The look a likes don't hold up..
This carb has many mod's that can be done. Go to JEG's or summit and buy a holley book. This carb really much like a #4160 but was made to stay within EPA limits.
Regardles of other peoples feeling's it is a good carb.
PS You should also have a Aluminum heat shield under carb. KEEP it
Caddy 53 chuck Centerburg oh