Why are my dougs 450 headers hitting EVERYTHING on my early a

I have had these headers in a 66 Cuda for about 15 years, they fit like a glove, I have had them in and out a bunch of times for cleaning and engine and trans change outs, never had a problem with fitment. I run stock 66 mounts with motor tied down, run a Borgesen power steering box now, have run a stock box as well, its a standard car and clutch linkage fits no problem. I also run 1.14 torsion bars and they are a squeeze and do touch a bit but it hasn't been a problem. I would try it with the stock motor mounts and check to see if the car is straight as mentioned above. You will need to unbolt the mounts from the cross member when you are installing so you can move the engine around a bit to ease installation, a floor jack under the oil pan will help you.