Go/Dan is a subsidiary of , or was bought by Transpro the radiator still has the same part # 431405 under the name Ready-Rad - Catalog - Here's the spec page. The Go/Dan Ind.,or parent company TransPro # 43 1405 replacement radiator has a 1 3/8" core.The stock one is a 1" core.
Don't worry about the additional 3/8" creating problems, of the extra core thickness 1/2 goes forward. The space between the condensor and radiator is reduced by 3/16".
3/8" doesn't sound like much, but that is 3/4" more surface area per tube. Multiply that times the number of tubes and it does add up.