When the larger fish that spawned upriver hit the dam, you can whack them right there just off the bank by the boat ramp by the dam. Clousers on a sink tip line have worked well for me in the past. I'd start looking for that to happen in maybe a couple weeks - although it could be a little later in June. When it goes off, I've found that you'll get at least a solid week of stupid awesome fishing right there in that area.
How deep are you fishing for them? I don't have a sink tip line but I do have some polyleader that I use down at the jetties by my school. How rough is the water by the dam? I've got a kayak that I want to take up there.
Not too deep - typically in that top few feet of the water column. I'm mostly using the sink tip to keep the fly pulling horizontal as I strip it. Like mentioned above, your poly leader will work fine, and they'll hit surface flies, too.
As for the chop, it's anybody's guess. It all depends on the wind. Texoma can get pretty rough at times, but if the wind isn't howling, conditions are fine. Early June mornings are generally pretty tame.