Edelbrock recommends their gaskets or an equivalent Fel-Pro, and I've used both without any problem. The key is that these recommended gaskets are soft enough to seal the aluminum manifold to the iron heads. Some gaskets are too inflexible and they will not provide a good seal.
The use of RTV instead of rubber seals on the ends is recommended by just about all the manifold manufacturers. You are just trying to keep the oil from leaking, and there is no real pressure to seal against.
Also make sure you use RTV to seal the inner bolts on the manifold. The threaded holes go through and into the lifter gallery and oil will wick up the bolts and onto the manifold if the threads don't have RTV. It does not hurt anything, but you will have little trails of oil on your brand new manifold.