I've seen a couple threads but none that really answered my specific question.

I just noticed today that the radiator in my 98 Gt has a small hairline crack on the top right. Looking around online I found a few options. 5/8", 1", and 1.25". Not sure which I have yet, does it matter which replacement I get?

I don't need anything special but figure for the price bigger is usually better. Am I safe just getting the 1"? I don't want to have to do any modifications to get one to fit.

Thanks in advance