Did you ever source a big shaft input for your toploader?
I should have at least 1
let me know if I should dig it out and take some pics

correct me if im wrong, but I dont think you can install a 351c intake in an FE engine? ,
and cant imagine anyone attempting to spend time and money to manufacture such.

are you looking for extension housing for use with 28 spline or 31 spline shaft??
and at what shifter mount position ? what size engine is in car?

I have various extension housings
Im assuming you have an FE where you will use the mid position mounting location?
is it for 28 or 31 spline main shaft ?

Ditch the pusher fan , get the biggest dia puller you can fit on the engine side.
If your upper pulley is limiting you in regards to available space between the radiator and pulley , there is a fan called sidewinder (made by Fanman) where the motor is not in the middle of the fan but off to the side where you normally have tons of room, and im pretty sure you can rotate the fan motor location to best available space.

Many other factors can hurt and help cooling:

Burp system properly to remove all air after the thermostat opens while filling cooling system you want to remove all air before installing the Rad cap..
Ive always drilled a small 1/8" hole at 12 oclock on the thermostat flange to allow air to escape while filling, starting it with the cap off watch or feel when the thermostat opens and slowly top off. You can also give it some rpm at idle to force any trapped air to the highest point in the system (the radiator filler neck).

if you live in a climate where theres no chance of freezing overnight , run more water than coolant (antifreeze). On the west coast Ive always run 80% water and 20% coolant , the coolant will be used for anti corrosion. Nothing dissipates more heat than water.

Run the highest pressure radiator cap that your system will allow , instead of a 12lb cap run a 16lb or slightly more depending upon your build and reliability of your system.
Proper Timing and properly adjusted carburetor always help.

If it runs hot on the street,  but cool on the highway,  then you usually have a fan issue.
If it runs cool on the street, and hot on the highway, then you usually have a radiator that is not big enough or has some flow restriction within the tubes

no dates, any other markings or codes
just the big font engineering number

more pics