Aluminum /6 Rear Main Seal

I am rebuilding an aluminum /6 225 and am trying to figure out the rear main seal installation. I have a Felpro neoprene 2-piece seal which is simple to install. What is confusing me is the (removable) upper seal retainer has a smooth outer surface while the mating surface of the block has a small groove in it. It appears like a seal would go there but none was included in the kit. Does anyone have any experience with this? Would I be safe just putting a bead of silicone or RTV sealer in it? Also, the same retainer has a recess on each end similar to the bottom seal retainer where the "L" shaped side seals go. Does a seal go there or should I just put silicone or RTV in it as well? Any help would be appreciated.