/6 to 360 rad swap

I am swapping my /6 to 360 in my 75 duster, from looking and reading on this site I new I had to change rads so I ordered an Spectra Rad to go with my swap, my question is when installing the rad, do I have to make any mods?, the Spectra I have does not seem to fit right in, is it possible that I have the wrong rad out of the box? thanks a bunch in advanced