Will a 74 nova steering column work in a 71 without any mods?

It should bolt in fine. Are you changing from standard to tilt? If so the harness plug will need to be turned over to insert it into the ignition switch.

No, Im changing from automatic column shift to manual floor shift. Column has no shifter.

The column will bolt in ok. From the factory the manual shifter had a rod that went up to the column that rotated the collar to operate the back up lights and lock the column only allowing the key to be removed in the lock position.
After market shifters for exernally controlled transmissions have an extra position on the reverse arm to hook up the linkage. Tremec and any other internal rail type transmissions will not.

Thanks Philip!