This is just a wild guess since what we got in the states wasn't called a 180B. I'm not sure what it was, I'm assuming it was the 610 here.
Anyway, deducing from Nissan's usual practice of naming cars for their dislacement in deciliters, why I'll never know, I'd guess that the 180B came with an L-18 four cylinder.
The one you saw in the ad might have been a conversion or a misprint. Or, I could have my head up my ass. Juan never knows.