For the cable...
Yes you shoulds look to Morse is there a Weller Truck near you
they can make up what ever you need (lengths,end types ect)
Thats who I use in My Heavy Truck Equipment Shop

 

BC847,
When I installed my 3200 spring for the 2nd time I cut one turn off and then bent a 1/2 turn for the connection point.
My throttle did the same thing yours is doing. One hash mark was too little the next one was too much.

I pulled the top off the IP and turned the throttle lever to WOT so that it was touching a business card against the cover - IE, there was just a hair of clearance before hitting the IP cover at WOT. I marked the top of the IP where the notch in the throttle shaft ( mine already had one so alignment was pretty easy ) was pointing and I put a dot on the throttle shaft at the same time.
After reassembling the IP I set the throttle WOT using a stick in the cab. Verified the throttle bellcrank couldn't turn much more - had about 1/8" additional travel....Then turned the shaft in the IP to WOT and set the throttle lever over it.
Took a few minutes of playing with the throttle adjusting rod but I finally got it adjusted so that WOT on the lever lined up correctly to the WOT marks on the shaft and IP top.

When I fired up the truck I adjusted the idle to where I wanted it using the low idlw screw.....It barely sticks out.

Now I know I've got WOT inside the IP when the pedal is on the floor in the cab.
Mine doesn't 'flare' like yours does, although it did when I first installed the 3200 spring.
I wouldn't swear to it but I'll bet your throttle shaft is turning past facing the spring which is actually pulling the spring out slightly rather than letting it relax totally...


Was any of that clear as mud ???

 

I run an auxiliary fuel cooler up front and I also have a cool can plumbed in for dyno purposes.

Id ditch the 3200 and just jump to the trimmed 4200. Great idle quality and plenty of rpm range. The pedal is just a little too touchy at times.

Wait, didnt you used to run a 4200 or am i thinking of someone else?

 

For cooling try dry ice in your cool can used it for years sand dragging its like a poo-rs mans nitrous