valve cover clearance

I had the same problem so I added 1 1/2" longer bolts and spacers to the heater box and cut the heater core tubes and soldered some copper tubing to it to lengthen the inlet and outlets. Were the heater box seals to the cowl i took 2 pieces of sheet metal riveted one to the top of the heater box and the other to the cowl with the factory seal then put a bead of silicone sealer between the two pieces of sheet metal installed the hook that holds up the heater box and tightened the blower housing to the fire wall let it set. I hope this helps