Just to clarify here, on #6UF cable, you cannot put this on a 55amp breaker. If you did pull those kinds of loads at that distance your voltage drop would fall far below the acceptable level. After reading your post I see your only running 120v circuitry. With that being said the acceptable voltage drop for 120v circuits is 3%. So I would highly recommend putting this #6 wire on a double pole 30amp breaker. At 30amps - your max voltage drop would be 3%. If your shop started pulling more then 30amps then your voltage drop goes up from there and that is when you get into equipment failure.
Again - I highly suggest that you install this on a 30amp breaker. Or possibly even installing the #2UF SER aluminum service cable so you can have a full 100amps available so when you do install more equipment, your covered. Good Luck!!