Plenty of filter info, but again...if the OP tries a number of filters without affecting his issue, he probably needs to look internally.

Filter debates aside the cast iron pump housing of the big block and the internal passages of the block really benefit from enlarging and chamfering the right angle turns to and from the filter.

If you think about the route from the pick up in the sump to the pump itself there is obviously drainback to consider and as the filter is horizontal there will always be a "heel" of oil in the pump regardless of a bypass/anti drainback whenever the engine is not running. Statically the level in the pick-up tube will be the same as the level in the sump with some residual oil in the low spots of the housing inlet.