Throttle cable not opening carb fully

Where is the best place to get or order one from? Also, when you say the correct cable, you are referring to the V8 cable....should I also look at the extension?

I cant answer every question. I can tell you there is a difference in carb location and operation for the slant and V8. With factory correct intake, carb, throttle bracket, and cable,,, good to go.
Aftermarket intakes and carbs may require more or different pieces in addition to those correct factory V8 parts.