I have never seen exact specs of the first generation 4000. According to the Smith book, the first ('57) basses had mahogany necks (with the dual truss rods system) and maple body wings, then the factory switched to walnut necks, and in 1960 to maple. The necks were wider at first and were narrowed in 1959. In 1961 the body is thinner, lighter, and more contoured - like modern ones, with the elongated upper horn.
The sliding bridge cover with the mute underneath it was introduced in late '57. Fireglo was available since 1960.
A friend of mine who played an early 4000 said that the body was thick and heavy and string action was high. I have read that among the 1st generation 4000's that survived, neck issues are not uncommon.