Razor is driving a Sunny, so NO engine mount mods are necessary. The A14 came in the Sunny STATION WAGON, so if you get one from one of these, the conversion from a Sunny [wagon] into a Sunny [other] has gotta be a doddle.

I believe that A15's are commonly seen in the smaller Nissan Vanette's & have a longer stroke to bump up the torque. In stock, or near stock trim, these commercial model engines will not really make your car much faster. A little quicker perhaps, but not much faster. I suggest the A14 option.
Chris
P.S.
The engine mount mod is only necessary when fitting '74 & later "A" series engines into '73 & earlier "B" series Datsuns & the chassis bracket needs to be extended rearward to pick up the engine bracket on the right side only. We wont go into the reverse option as very few will fit an A10 into a Sunny Wagon.