The 89 hyd roller cam 318 I just dissasembled has shaft rockers and hollow pushrods. I really don't think enough oil would get past the rocker end of the pushrods to affect oil pressure or "empty" the pan cause too much oil was going to the top end. If its a race only motor where you are concerned with oil windage there might be a small affect on that.
And if it is a race motor I don't think u would be useing a 5/16" pushrod there would be a lot of flex in a 9+" 5/16" pushrod.