Will a radiator from a 15 fit a 19?
Yes and no. Yes it will fit the frame. No, it will not fit the hood. The upper radiator hose neck will not line up across those years either.
Drive carefully, and enjoy, W2
Will -- The '15 radiator will fit with the '19 body, but as Wayne said, you'll need to replace the water outlet, as well as the hood and hood former.
Lots of later bodies were '15-ized, but it takes a lot of parts to make them look right. All the above, plus all 4 fenders, the splash shields, etc.