im looking at getting a fixed crank for my bike, all i know is it is a lotus bike roughly in the early 90s i think.

it looks like the pic i provided.
now what im trying to do is figure out how to measure for the correct sized BB so i can get the right fixed crank for my bike or if i can use my old one. the crank size i want is a 165-170mm with either 44t or 46t if that helps. any help would be appreciated.
thanks!