a904 and carb help!

Yes, pictures. You say the linkage is home fabbed so we don't know what it looks like.
You keep saying you want a carb with the kickdown linkage like it is supposed to be sold that way. The linkage is a factory part setup from The car manufacturer.
This has nothing to do with the carb manufacturer.
There are many, many different factory stock linkage parts out there. There are none for a 340 with a 904 trans. The 340 always came with a 727 trans.
The easiest way at this point is to go with an aftermarket, adjustable setup. LOKAR is one of the most well known.
Lokar : Throttle Cables & Kickdowns
727-904kd.png
Here is how to correctly check the fluid level 904 and 727 follow the same procedure:
727 Fluid Level.