it probably wont work too well, since the 55 gallon is nearly twice as long (if it is the basic rectangle design) it wont be long enough to cover from one end to the other with intense lights, it will still probably light it up but you would have to stock any corals etc directly underneath the lights since it will be where the most intense light is, out to the sides will be lit but it will be very underlit for any kind of coral life, its just not enough watts per gallon and its not spread out enough. you would only have about 2 watts per gallon...not really enough.
if you have the lunar lights i have a 24 inch one id trade with you and then you would just need to buy one more 24 inch which is cheaper than a 48 inch strip...then you could have two 24 inch hoods...which will be about 5 watts per gallon, which is basically the same as buying their 48 inch hood since they use four bulbs instead of two.