Have you got the new pins? If not maybe you should look for complete
hinges. But remember, if you use heat, you are NOT heating the NEW pins.

A couple things to remember about using heat:

1. Don't use more than necessary to achieve the desired objective.
The more you heat it above about 500°F, the more you temper (soften) the steel.

2. In using thermal expansion to loosen things, remember it is the temperature
DIFFERENCE that does most of the work (although you do also dehydrate the
hydrated iron oxides [rust] that may reduce their volume). Therefore it is
to your advantage to heat suddenly and act immediately when the part is hot,
before the heat conducts to the inside part (the old pin). If you can have
the hinge in the press with pressure applied, and turn up your torch pretty
hot so you heat it quickly/suddenly, you'll have your best chance of
breaking it loose.

I remember once my grandfather watched from a distance as I worked with a
torch for a couple days trying to get a brake drum off my 1940 Ford pickup,
similar to the arrangement on the 122 but with a much longer tapered section
on the center of the hub. Finally on the third day as I was getting the
torch out again he came out with a teakettle of boiling water and a rag.
He said "Got your hammer?" I protested that I did, but that I had had the
hub almost red hot several times already. He said, "OK, get ready." and
wrapped the rag around the threaded end of the axle and then poured the
boiling water over the end of the hub. As soon as he had poured all the
boiling water over it, he took the rag off and said "OK, HIT it!" I did
and the brake drum popped off. With the boiling water, which has a very
high heat capacity, even though it isn't extremely hot, you heat the hub
suddenly, and for a couple seconds, before the axle inside gets hot, it
is a little bit looser.
--
George Downs, Bartlesville, Oklahoma, Central US