What radiator?

Help please. LOL

I have a 1968 Plymouth Barracuda. The car had a 318 and now I am installing a 360 mild build. I no longer have the original radiator. I am looking for a cheap one that will work in this car. My problem (this is where I am hoping someone here can help) is I don't know what size I need. I am sure there is nothing at the local junk yards for my car and I need to know what size and any other info I can get. If there is anyone here that knows anything and willing to help I would appreciate it very much.

Thank you

Brad