85 4x4 intake help
 

I have a 85 silvetado 4x4 with 350 auto 6 in lift and 35s I had a bad oil leak on valve covers so I replaced them with tall alum ones and new gaskets now it still leaking from back of motor and was told it was intake so I got new gasket but need advice on puttin them on and if I need silicone or not thanks for any help