Crank advice

I'm after some new cranks and have narrowed it down to two options. Either http://www.freshtripe.co.uk/Freshtripe/Shiny%20Bits_files/Sugino%20RD%20Track%20Crank-1.jpeg for £47.50 and buy a basic bottom bracket, or http://www.pearsoncycles.co.uk/product/3230/FSA_SINGLE_SPEED_CHAINSET_AND_BOTTOM_BRACKET_OFFER with the bottom bracket. I'm leaning towards the Sugino because I think they have a nice look to them but does anyone have any experience with either and could give me some advice?
also with the suginos, tokyo fixed gear recommends a 103mm bottom bracket but freshtripe says a 113mm would be best. Does anyone know which of these would be correct?
Lastly when buying bottom brackets what does the second number (either 68, 70 or 73 re3fer to and how can i tell what size is best for me (i dont know what my frame is as it was bought second hand)
Thanks in advance

The other number is the BB width. You can find out yours by measuring it

The other number is the BB width. You can find out yours by measuring it

Yep it's your shell with, 68 mm for iso / british 70 mm for italian

buy the bb when you know what cranks you're buying.

I am using the Sugino and a 103 would be the correct one. I am using with a 107 and the chaninline is a few mm's out.
The problem is that the cranks are not track specific (i.e they are built for two chainrings - one on outside, one on inside)
So using the outside position (which is best cosmetically) throws it right out.