The crank length and chainring size really don’t impact the bottom bracket compatibility. You should be fine. I gotta say, going from a 155 crank to 170 is a large jump. Why? Did you buy the bike used?
There are different spindle lengths for square taper BBs. You need to get the correct length to put the arms in the right spot. Phil Wood, as an example, offers a very wide set of spindle lengths from 103 up to 145. White Industries offers fewer options at 108, 113 121.
Also check your BB Shell width (most bikes will be either 68 or 73mm; your fat bike will likely have a wider shell than either of those), and if the crank has JIS or ISO taper.
The crank will have a stated BB length to give a standard chain line, ie the crank is what makes the choice. If you want to change chain line for some reason you can change BB length but otherwise refer to the crank manufacturer for BB length. If you’re planning to fit on a current BB and it’s similar (not double instead of triple or anything) it’ll probably be fine though.
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