utilitarian wrote:
....

I thought I would be able to just lift the gate off the hinges,
but not so. After lots of Liquid Wrench and "3 in 1" oil on the
hinges, I was able to move the gate up about an inch ( separated the
hinges about an inch), but it seems to be stuck there.

You're not using a big enough hammer, then...just drive 'em off although
would probably help to get a lever under the gatepost and have somebody
help take the weight off while you're doing it.

If, as somebody suggested the tops have been enlarged (I'd guess it's
not really very likely, but possible) put it back down in place and use
a piece of coarse plumbers' emery cloth 60/80 at finest or a file and
clean them up a little.

I want to reuse these hinges in my new gate, if possible.

What could possibly keep you from doing so other than simply throwing up
yours hands???

My main question is ......... how accurate do I have to be in
installing these pintle type hinges into the new post and gate ?

Close enough to put the gate back on them...

Is there a method to make sure everything lines up properly?

Yeah, measure where you want them to go and put 'em there--this ain't
rocket science here, it's drilling two holes a fixed distance apart at
the right height...

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