You should get better than that out of it. But 20 - 22 mpg will be about it with an auto. You would get a little better with a 5 speed manual. Tuning is critical on these. Timing, points gap and carby float level need to be spot on. The electronic ignition from a later model will help and doesn't change the appearance under the bonett that much.
Mine gets about 25 mpg on average now. But I have a 1uzfe and 4 speed auto in it. The paint was a bit faded so it got a respray. Apart from all that and a brake upgrade it is all original. Not quite as tidy inside as yours, but still pretty good, same colour too. My plan was to keep it looking as original as possible just with a more modern engine.
It drives as good as any newer car now. Very quiet on the highway for a station wagon.
Shane