Everyone has an opinion, so here's mine. As you've already gotten safety belts, the next two issues I would address would be a dual circuit brake master cylinder and an energy absorbing steering column.
The old girl cleaned up real nice though.
Strong family resemblence to my first car. A 1957 Ford Fairlane 500 4 door sedan, bought in 1974. 312 V8 "Thunderbird Special" on the rocker covers, 4 barrel carb, and an automatic. It only used second and high for normal driving. You had to put it in Low to start in first. It got about 12 mpg.
That made me think, does your car have electric or vacuum windshield wipers? Vacuum operated wipers pretty much quit when the car is under much of a load, and I have no idea what boost would do for their operation.