Will a 1978 C10 TRUCK steering column fit 1975 c10 TRUCk?

While both are C10s from the same generation, there's a *chance* they might not be directly interchangeable. Steering column components changed slightly year to year, even within a single generation. The splines on the shaft, the attachment points to the steering box, and the ignition switch wiring could all be subtly different.

It's best not to assume compatibility. You should thoroughly compare the columns themselves before attempting installation. Look for differences in the shaft diameter and spline count, as well as the mounting points and electrical connections. If there are even minor differences, it might not fit correctly or safely. Using an incompatible column could lead to dangerous driving conditions.