I haven't worked with (or on) a kickdown cable setup (yet) but the simplicity and the
cost involved to find the "correct" parts (and not what someone is peddling off as "correct" parts - which are far from it).
With the air cleaner in place, the cable setup is almost not viewable (for the most part).
The front shaft (primary bore) of 4-bbl is further forward than it is for a 2-bbl. That means the vehicle needs a longer throttle cable and a longer kickdown link. The throttle attachment if further Left (of center-line of engine) than a 2-bbl is, by about 1-1/2 inches (or so - not measured). That means the throttle cable attachment needs to be further Left, as well.
A 318 2-bbl Throttle Cable bracket (from my '86 Fifth 318):
The 2-bbl throttle cable (barely viewable because it is under the cruise cable) adjustment flange is sorta parallel with the ground (yellow arrow).
On 4-bbls, that tab is mostly sticking straight up (but hard to tell in this picture):
A person can bend flange up and get your original one to work. It doesn't take a rocket scientist to do this nor does it need to look anywhere perfect to operate correctly. The import part is to try to keep the area where the cable and clamp attach to, unbent.
The next part is the upper link. The 4-bbl link is ~1 inch longer (a rough guess - not measured).
ALL 2-BBLs - the upper link is bent upwards at the rear and the rod goes in towards the Left fender. You can see the direction in the top picture, but you can't see the "upward" bend at rear of link.
ALL 4-BBLs - the link is (also) bent upwards at the rear and the rod goes in towards the center of the engine. This is a poor picture, but you can see the upwards bend in link (green arrow) and the direction the link is pointing (pink arrow):
The upward bend (in upper rod) is so it will clear the throttle cable.
The picture above and below is correct rod for a 4-bbl. To take an existing 2-bbl rod/link and convert it to a 4-bbl then cut it at the white line (below), rotate it 180' (to as shown) and re-weld:
Then, cut at yellow line. insert another rod roughly 1 inch longer and weld into place. Measure your setup before cutting/welding! (measure twice and cut once). You have a lot of adjustment at the turn sleeve - but not enough to convert a 2-bbl link to use for a 4-bbl.
These two mods should get you working as far as kickdown linkage is concerned.
The next item is cruise control (if applicable).
2-bbl small blocks use a "L" shaped bracket to attach the cruise cable in place:
4-bbl small blocks use a different design:
A person can straighten your "L" shaped one to a more flat design. The 4-bbl cruise bracket adapter (above) is rather hard to find.
The top picture shows a proper 2-bbl setup kickdown setup (with cruise).
This picture shows a older 340 setup (but very close):
If you notice, the rod also has an outward bend to it as well. This bend is not as critical.
Hopefully, I made the muddy water a bit more clear.
BudW