I bought an old n scale pizza hut. It was made in the 80's. I put it on the layout, and it looks z scale!! Since when can a pizza hut fit on an average bulkhead flatcar?
Maybe on of the original buildings. I read once that the owners came up with the name Pizza Hut since the sign on the first place they bought was so small it did not allow for more than 9, 10 letters.
I would not worry about the overall size of the building. One of the better ways to check if a building is relatively in scale is to measure the size of the door(s). This should tell you if it is about right. If yes, then it is just a small building (it's Pizza Hut not Pizza Mansion ). If not, then use the building towards the back of the layout where it will help with forced perspective.
Looking at the size of the building to both the car (automobile) and the bulkhead flat car i would say that it is N gauge. The flat car has got to run out at around 50 feet in length so you would indeed be able to fit a small branch of pizza hut onto it.
As for the comment above re: pizza mansion, LMAO but it's true, some of the branches of Pizza Hut over here are comparable in size to maybe a 40 seat diner. But as suggested the size of the door will be the telling factor, should be in the region of 15mm high by 6/7mm wide (approx).