Is 3" too thick for a rad?

Do you remember what clearance you had with your old unit? You probably will have enough room but you may need a different spacer or clutch. Just depends on the car and engine combo and A/C can make a difference too.

I`ve got a 28x19 crossflow a, alum. radiator that is 3" thick in my 440/505" fastback, 1/2" fan spacer- mech. fan, no clutch.