rear windshield gasket

I bought a reproduction rear winshield gasket WS303 from year one a while back and am now getting around to install in on my 67 notchback. Year one says "Can be used on 1967 models if later model reveal molding and clips (# A906725) are used. I put gasket directly on rear windshield there is a gap, don't know if I need to use more then just reveal molding or lockstrip, need some advise were I should go to get the best snug fit for rear windshield.