Yes, I put a skim coat of RTV on the surface where the cap bolts to the block--most of it will squeeze out when you torque it, but it keeps oil from seeping out between the cap and the block. On a 300 engine, I usually torque the cap, then put the seals on the sides, but on the 401 they were so tight I couldn't get them to go all the way in with the cap installed, so I had to put them in the groove on the cap, then install the cap. It is tricky getting them to stay in place and go all the way down while you install the cap, so it will take some patience. If the nails won't go all the way down, I would just trim them off flush. If they won't go all the way in, it is because it is too tight in there, which means it is sealed just fine--especially with having RTV all over the seals when you put them in.