Bolt Size for Water Neck and Ignition Coil

I replaced my stock 2bbl carb and intake with a Edelbrock 3776 Intake Manifold and Edelbrock 1405 4bbl carb(pending installation). For some reason the bolts for the water neck and ignition coil do not fit this manifold (3776). I tried them on the old manifold and they go all the way down. I took them to my local auto parts store and was told they were 5/16 bolts and I got both thread sizes and they still do not seem to fit. They said that since its an aftermarket manifold they do not know what bolts I need. Does anyone know the size that I should be looking for?:banghead: