I have a 70 Challenger with the same kit that is kind of a resto mod like yours...but not as nice as yours.
Here are a couple suggestions that may or may not help. Since your car was an originally a 4 speed car why don't you try the mechanical linkage. I thought the hydraulic set up was for people who were converting to auto and didn't want to deal with installing the linkage.
Another thing you could try is get rid of the pistol grip and use a ball handle. I bought a used 7" hurst handle with a ball handle for $20 and it makes shifting a lot more natural for me compared to the pistol grip but I don't shift any where near 7500 rpms.

My trans also interferd with the tunnel...I think most e-bodies do on the right side. I just clearenced it a bit...