I once had an  original'82 diesel radiator(not really much different from
gas). I took it to a radiator shop for some forgotten reason and the
technician inspected it. He pushed his fingernail right through the thin
water passages, again and again, totally destroying my radiator. He told me
that over years, the road salt will eat away at the lower portion of the
radiator, from the outside, in. When that happens, the radiator is junk(He
kept that radiator). I then pushed my fingernail through it--Wow! Check to
make sure that yours is not at the end of its life span in this fashion
before sinking lots of money into it. I suppose that you could take the
pressure off and add stop leak if you are far from home when you discover
this, but others wise, expect to shell out for a new one.

New ones don't exist, as far as I know, and they changed it in '83, I think,
to match the gas radiators. The core of the gas is the same as diesel, it
looks to be, but I never tried to swap a gas core to diesel tanks. BusBoys
once sold an early diesel radiator for $600, but it is NLA. Talk to a
radiator shop about it it? If it were me, I would attempt to swap it as I
said above, as the mounting for diesel and gas radiators to the vehicle is
different. Also, that long down tube on the diesel radiator that you have is
probably perforated(or about to be)at the bend. Just braze it up. People
here commonly change to gas radiators, but I never read the postings about
how they did it. That is probably what you want to do. An '82 radiator, if
you live in the salt belt, is not too reliable these days. Good luck.