If you read the pro-motorsports web site, you'll see that they talk about a 2" drop of the UCA mounting points for the best geometry ('69 and '70 models only IIRC). I have no idea what that means as far as the science of suspension goes. I know you want camber gain, but I haven't measured, sketched or calculated anything to see what exactly the change does.
My answer is: I would be very surprised if it created any problems. You just won't get the handling benefit from the geometry change. You will get a handling benefit from lowering the car, though. So the end result should be improved handling even without changing the UCA mounting point.
One thing on my car, when I did a 2" relocation and added homemade wedges I had to shim the UCAs out from the shock tower to get the correct camber. Otherwise I had run out of adjustment from the lower control arms. You may find with lowering your car this much that you have a similar problem.
I found a place (edit: AMK products) that sells the original style press in bolts that attach the UCA shaft to the shock tower. If you have to shim very much with the original bolts, you will run out of length. However, the 65-66 UCA bolts are 1/2" longer, since they are meant to be shimmed. I will be using the 65-66 UCA bolts in my car.
