Radiator replacement

The unfortunate part of these suggestions is that good radiator shops are going the way of the dinosaurs, dying. I used to have two very good choices in my rural area, now I have one, part-time one.

Our throw away society isn't always better.

Recore is the way to go. I had it done on Prevost for 1/3 of what new one would cost.
If you had overheating before, you can order new core with more rows.

I needed a radiator for a 1944 bulldozer a few years ago. I took it to a radiator shop, they measured the core found it in some book and ordered it. They put my top and bottom tank on the new core and it cost me about $500. Are your tanks good?

You may not like my answer but;
I have a 1990 Fleetwood Southwind gasser. I needed a new radiator for the rig. After much searching for a pre-built radiator I had the old radiator removed and a NEW ONE BUILT.
I dealt with a local radiator rebuild shop called LILAND radiator. They have been in Syracuse for about 35 years. The radiator was made from all new parts. The bad news is $2500.00 for the new radiator. That is just for the radiator not anything else.
The exact name of the place is Liland Trade and Radiator service
3154320745

There are radiator shops just like tire shops and they'll be able to point you in the right direction, or even repair yours. Online there are numerous custom manufacturers, like This one

You can also google RV salvage and try to find one in a salvage yard.

A few years ago, in the summer, I took a trip up to Fairbanks, AK and all along the way, I had to keep topping off my expansion tank. So I went to a radiator shop there and found that they could remove my rad, rod it out, fix any leak, and replace it for under $300. But they were short of work at the time. Also, they couldn't spot a leak on the rad and told me they didn't think it was leaking.

I didn't get around to it, but years, and a couple-three gallons of wasted 50/50 mix antifreeze later, found that one of the heater hoses from the engine up to the front of the RV had a slow drip-drip-drip leak. Right near the front of the RV. Luckily, diesels all have shut off valves for that at the engine so I drove around for another couple years with no heat. But I'm a snowbird so not a big deal.

Good luck...