1964 Ford Thunderbird Power Steering Fluid

your vehicle is designed to run with type A transmission fluid, not made anymore.

you can use type F or type FA instead if you can find that either.

others choose to use power steering fluid instead, but its thinner and you may develop lots of leaks.

but using different kinds might not work well together so you will have to flush out the whole system. refill and bleed of air.

good luck