you have the right idea, take it apart, carefully file off the casting parting lines and any sharp edges in the air path. This is basically deburring work, don't get carried away.

Trial assemble the 3 carb body parts together without the gaskets and make sure they align without big overlap "steps". You will find mis-match / overlap so grind that away.

Now check the gaskets, you will find that the gaskets will hang into the air path, use a sharp exacto knife or razor to trim this excess gasket material away.

You can work down the throttle blade and shaft as you described to help WOT airflow. Basically, just look down the carb. as if you were air and smooth over what you would bump into.

Clean and blow-out all passageways and reassemble with a high quality rebuild kit.
DD

"Basically, just look down the carb. as if you were air and smooth over what you would bump into..." Having been called an airhead many times, I feel well qualified for that task.
Thanks, Doc!

before you start filing away, chk the sealing surfaces for flat with a good straight edge. Sometimes you may need to flatten the air horn/bowl cover in a press, to get it close, first. Be careful, those things are just cast zinc. And be careful when you tighten them back down, or you'll be right back where you started.

_________________
'66 Cuda 225/4spd
'66 Dart GT convertible 225/auto
'64 Dart GT 340/4spd

FYI.

One of the notorious problems plaguing BBD's out of the junkyards are the throttle shafts tend to leak and need to be rebushed. I don't like to see a puddle of gas on my manifold at idle...

-D.Idiot

i got my 2 barrel holly off an old 318 that was sitting in a junk yard and it was pretty easy to rebiuld all it takes is a little time. i put it on my 1979 valare and it runs good.

i have a 1978 plymouth valare that hase a super six in it and i can't find any parts and hints

it's likely your carter has multiple gasket surfaces that are warped from heat and over tightening during rebuilds. unless these surfaces are machined your carb will leak gas and air in all the wrong places. polishing the air path and removing casting marks will probly not get the uumph your after until you address the warpages.