Yes you definitely need that. Without it the trans will short shift when you are under hard acceleration because only the governor will be controlling the shift points. That kickdown rod is connected to the throttle valve in the transmission the throttle valve works in opposition to the governor prolonging the shifts when you are under acceleration. Your life would be much simpler if you could locate a kickdown rod from another truck just like the one your engine came from. The geometry on those things is specific to each engine-transmission combo. If you can't locate the factory rod Lokar makes some real good cable kits you should call Summit and talk to a tech guy just to make sure you get all the correct parts that will work together with your engine, trans and carburetor.

 

OP doesn't know what the 460/C6 came from, so it could have come from a:

1968/78 Passenger Car, 1973/79 F100/350, 1975/86 E250/350, 1983/86 F250/350. 1987/97 460's have EFI, 1989/97's have E4OD

There are 4 different 460/C6 kickdown rods used in 1973/79 F100/350's, which one will work in a '66 F250? Probably none of them, so the OP will be better off using a Lokar cable.

And if this combo is from a car, there's another surprise awaiting the OP: The manual control selector lever. A car lever will not work in trucks.

 

You are correct ND. There are a gazillion different kickdown rods. And I wasn't going to mention the manual lever since there are about 2 gazillion different ones of those things. But he did say the engine and trans came from a truck so I figured he knew what truck they came from. And old guy, "at the time I was young" told me to never ever throw away a kickdown rod because you will never find a new one when you need it.

 

 

You would only notice it if you were climbing a steep hill or when you needed the transmission to kickdown a gear to pass something. That rod only comes into play when you are getting near wide open throttle. Without it the transmission will shift based on the rpm of the output shaft regardless of how much throttle you are using. In other words imagine you are doing a big burnout at a red light and before you even get it going good the trans shifts into second then third and the reverse/high (direct) clutch turns to toast. That is if the forward clutch doesn't give up first. And you are going home on the hook.