I've been looking into this as well. I would like to run a valley plate with my six pack setup too. However, all the valley plates I've found are flat across (except one modified for one particular intake). The six pack intakes "dip down into the valley" of the valley pan. I never considered grinding off a huge section of the bottom of the six pack intake, but I suppose that would work. Many years ago I basically made my own valley plate by cutting up a stock valley pan and using TONS of RTV silicone and I sealed the intake runners with one set of paper gaskets.

Be advised....you "probably" won't need any of those paper gaskets although every old Mopar book you read says you need them. My block was decked .040" and my heads .020" (fyi). I was unable to use even ONE of those gaskets on each side, let alone both gaskets. My intake barely bolts up with ONLY the factory valley pan.