About to install my rebuilt Holley 4160(1848-1) carb on my 1956 Crown with 292 CI-v8. I have been using various Holley carb videos on youtube to help with the rebuilding and installation. On may of the videos, a throttle return spring - sometimes a double return spring is installed from the carb throttle linkage to a fixed point around the bell crank area is used to return throttle to the idle position. I only have an accelerator return spring located vertically along the firewall on my setup.
Do I need to install a separate throttle return spring in addition to the accelerator return spring? How was it designed from the factory?

Thanks
Danny