A WD-9 radiator will not fit.
Yes, it is expensive to get one re-cored but definitely worth it. It will be fixed once and for all--no more problems. I have installed a few used radiators and they are usually plugged up or they leak. Sure they were cheap and available, but not worth the headache. A properly recored rad is as good as new and it will fit the tractor properly unlike an aftermarket one.