my 122 had problems cooling. I took the rad apart, cut some wooden sticks to just fit the rad tubes and pushed all the stuff stuck in there out..
I removed both the top and bottom, If I did it again I'd try to just remove either the top or the bottom.

after back together I put it in a sink and pressure tested . i had a couple of spots to chase with a torch and re solder but not too much..
If you want to spend, a rad shop can do it for you..

in my cae that made a huge difference , I went through similar issues in my ford van and in that case just opted for an aluminum rad.. it works fine but if you care about originality I'd keep the orig fan and copper or brass rad
the rad shop I went to with my ford rad had a tank of molten solder, makes getting it apart easier. I used a plumbers torch and just circled the seam until it came apart. I tinned the mating parts to make sue they would solder ok before I put it back together. I think selling a new ford rad meant lass labor for him..but he was capable. it was on first in Burnaby, a couple blocks west of boundary road..

I needed a water bottle so I soldered up a 2" tube of copper with a cap ont he bottom and think I used a 2":1" copper pipe reducer, then fitted the parts , probably from an old rad so I could put a new rad cap on...
the OEM rad has a a cap but it doesn't have a pressure relief valve. if you remove it and look down you can see some of the ends of the tubes. My take is those are plugged up. I used good old lead solder not the new style lead free solder.

i removed top and bottom but if I did it again I'd pick and just remove one or the other. I cut wood sticks on my tablesaw to fit fairly loosely and went gentle at it , you can always cut a bit larger sticks later.. If you are inclined to DYI It can be done, you can take your own appropriate cautionary measures about the lead solder being poisonous.