Can you replace the steering arm on the steering box?

just swapping power steering into my mazda but the bolt that connects the steering box to the center link is sheared off on the power steering box, so im trying to swap the arms from the manual to the power box, but am having no luck getting the big nut off can't get it to budge, looks like its meant to come off but I can't get it?

have u tried to heat it up

Don't heat it! Unless you want to run the risk of cooking the seals.

You need more leverage... put a cheater pipe on your breaker bar.

Are you talking about the pitman arm?