Steering gear box for 75 duster /6

Hello everyone,

I've been having a hard time finding a power steering gearbox that will fit in my 1975 Plymouth Duster. I've ordered one from advance auto and from a local parts store but they send a different one than the one shown in the pictures. And the ones I find cost an arm and a leg. I got a quote today to rebuild the one I have but they wanted 600. Any and all help would be greatly appreciated.