In 77 I believe that was all that was offered of the V8 motors. However, there were different breeds of each motor. For example, I know you could get a 350 V8 from 150HP all the way up to 175HP in a truck back then. 400s were different animals anyway and they're so rare that you never know what breed of 400 the motor is in the vehicle until you look up the RPO code.
For example, mine is the 350cu 175 horse LS9 motor.