If he's putting you on sora cranks & also a tiagra front derailleur... just go with the stock long haul trucker. The custom build doesn't seem to be upgrading your components much (or at all...)

As for crank length - I'd say use the 165 mm cranks. You'll be fine. Shorter cranks are a bit easier to spin, harder to mash with. And they're gentler on your knees.

I'm 5'1 and have changed all my bikes to 165 mm. My knees feel 170 cranks a bit more.