Does your car have or come with A/C? I could be wrong, but I am almost positive that the only firebirds with the thermostatic clutch where the ones that came with A/C, that along with the 7 blade 19.5 in fan. If no A/C, it should be a 5 blade 19 in fan (power flex) on 400 V8's. Also, you might want to ensure you have a good working rad cap that is a 14-17 PSI cap. This will help a good deal. I am also not sure about the 4 core, there has been some debate about them, but I know my 400 (A/C car) came with a 4 core, I cant remember the exact specs on it, but I think there were two different sizes of 4 cores, one being 23 inches long and the other 21 inches long. I know some came with a spacer, but I dont know exactly which ones, but I do know the 400's with A/C didnt. Hope this helps you out some.