the 54-tubes are available in 2 sizes:
1150 mm is standard, some vendors also offer a short version (1047 mm)
the light bars is a little longer than the tubes, of course, these are the dimensions:
http://www.aquariumcomputer.com/Syst...ight_bars.html

you need a light bar with BP-option, the length of the light bar depends on the space you have in your tank