Jerry,
I saw, in the last week or so, those exact vents on ebay. I will try to find them again and post the link.
I did have mine re-chromed. They do come out nice.
As far as an exhaust blower.. The vents in the rail on the side (the ones you are missing) and the ones aft are for natural ventelation. The blower I have is the original set up and is the standard I think on the 38. It is screwed to the hull on the port side just forward of the tank vent. Access is from the locker in the wheel house. There is a ss louver screwed to the outside of the hull. On the inside, the 4" vent hose is run under the deck and then down into the low part of the bilge.
Any of thos PAR or Jabsco blowers are ok. I think mine is a Jabsco.
Geo.
ps if the grammer or spelling is a mess it's because I'm home with the flu.