Looking to buy a 150. Only problem is that I need a 550lb useful load. Book values for years 62-65 and 71 state that this is possible but reality states otherwise.
Well Jeff, as it looks like you have already summized, speaking from a truely legal stand point, that would require an empty weight of 1050 pounds or less. Pretty light. You might also want to keep in mind that the 62-65 150's have limited baggage room. So, if you want to keep legal on paper, you Probably would be better to be looking at a different airplane.
Now, speaking from a purely practical stand point, depending on your flying conditions, the 150 will carry 1670 pounds or better quite safely. Making it more plausable to carry your 550 pounds.