What trucks are "these trucks"? (always state year/make/model, if pertinent to your question/post)
I think that turn signals became standard equipment on trucks in the late 50s? Factory-installed Optional turnsignals on trucks first became available in 1954. GM accessory turn signals were available for trucks for many years before 1954, and the wires ran inside the steering column, exiting the column low under the dash.
We need to know your year/modell/size truck to answer the u-joint lube question. Until 1954/55 u-joints were inside an enclosed drive-shaft "torque-tube", and were lubricated by transmission fluid (from the transmission). In 1954, the 3800 u-joints were not in a torque-tube. They had grease fittings. What document did you read regarding u-joint lubrication?
