There are 2 easy tells for me concerning 8N's. All have transmissions with 4 speeds forward/one reverse. All have a single nut about 2" across the flats holding the rear wheel hub to the axle shaft. 2N's and 9N's have neither feature. NAA"s have the axle shaft nut, but an overhead valve engine.
N series serial numbers are only found on the engine cylinder block. A replaced engine clouds the picture considerably.