An update - just for anyone looking at recoring their radiator.
On a member's recommendation I eventually decided to use Phoenix Radiators in Wodonga. My old radiator had to be posted but that wasn't a big issue. Austpost was $19 each way and border closures at the time made driving risky.
Phoenix sourced a 3 row core but could only get a 13 gills/inch rather than the original 16 gills/inch. The actual tubes appear to be larger than the originals so it might compensate.
Attachment:
3 row core.jpg
Clayton at Phoenix was good to deal with and seems to do a lot of classic cars. He replaced the original cracked filler neck with the same longer old style type and kept me up to date with progress.
I primered and painted it when I got it back, about 2 weeks later. All up it cost $550 plus freight. It isn't back in the car yet but looks a very neat and professional job. I know there are other options but I was interested to see whether repairing was an option today.
Attachment:
Radiator mini K.jpg