stock carb hp500, gil, where does the water mix with the exhaust gas on the riser? at the fitting or is the riser/elbow double-walled and enter right before the tail pipe, would I help prevent reversion and possibly increase power if I had the water mix as far back as possible-such as at my Teague switchables, does anyone make this?

Would using a dry exhaust with mufflers and dumping the water on the drives and eliminating the drive shower pickup, add speed or is it not worth the $$ and effort?

The water already dumps about 2" before the end of the tailpipe. I don't think you would see any increase in performance by running dry. Just a LOT louder.

You can get riser elbows that are a smooth bend, not a U-bend. This will help power noticably and will not hurt or help reversion.
Griff is correct.