A restrictor on the feed side will slightly improve oil pressure on start-up since it delays filling the filter up.
It also protects the engine if the filter or housing leaks - which would otherwise drop system pressure if the restriction was in the return line to the pan.
If your housing drains out, you can cure that by simply making a new longer return line that loops up higher than the filter and back down to the block drain. A simple piece of brake line will do.
