I need suspension EXPERT opinion

Here is my build. I have a 63 valiant pro street with an Alterkation front end, a 400 big block and 7 qrt oil pan, coil over shocks with 450 springs. My problem is inorder to get my oil pan off the floor 3 plus inches I have to crank up on the springs making my front SOOO hard there is no rebound on the springs. It feels like I have solid rods instead of shocks. The shocks are 14 inch when fully extended. Currently they sit at 12.5 inch and info says fully compressed are 10 1/8 giving me 2 3/8 of travel. I do not have tunnel clearance to try and raise the motor mounts. There is not enough travel between the upper and lower control arms for longer shocks. I am waiting for a response from RMS on what they suggest. Any thoughts???