I have a 1974 F250 Camper Special, 2WD, C6 Automatic, with a 360. The truck originally came with a 390. I cannot find the correct speedometer cable for this truck. The connections do not match up and if I do find one that looks like it might work its not the correct length. Does anyone have any solutions or am I just overlooking something?

 

There is no external dimension differences between the 360 and 390 so that is not your problem. How is the cable routed?

 

It snaps into the back of the speedometer and runs down and is supposed to screw into the front housing of the transmission. All the cables that are being shown show that it pushes into the side of the transmission and use a bracket to bolt it in place. On my transmission there is only a threaded housing that the cable is supposed to insert into and then you screw down over the cable. The only thing I can figure is that the transmission has been changed at some point and that is why things are not matching up. Even the cable LMC is showing isn't right. The part that attaches to the speedometer is correct but the other end is not.

 

The speedometer take off on the C6 is on the driver side of the tail shaft. On a mechanical transmission you need to take the speed from the tail shaft. My guess is someone has changed out the transmission and you're seeing the plug for the torque converter lockup. I believe LMC has the quick and easy transmission ID pictures of the pans for ID purpose.
As a side question, how do you know it is a 360, did the po tell you that?

 

I ended up finding a place in the area that custom makes cables so we were able to get a cable made with the correct connections on both ends. They only charged about $50 and they took care of it within 15 minutes. Based on the VIN it was supposed to have a 390 but what the engine is showing it is a 360.