Mine are 14 years old and just sent them in to be checked.They are still in excellent condition and I have a 242/252 @ .050" with a 112 degree LSA roller cam and no reversion. They seem to have a good drop from the bend to where the water is introduced. I've never seen a complaint on OSO, they'll be on my next boat.

Ss steel or steel headers
 

Are the headers that you folks have had good results with made of steel or stainless steel

Mine are steel.

Mine are Steel also.

Yours are actually steel on the outside tubes and 304L stainless on the inside tubes:
"Our fresh water header starts with mandrel bent 304L stainless steel interior tubes. The standard tube headers use 2" OD primary tubes. Our big tube headers use 2 1/4" OD primary tubes. The exterior tubes are mandrel bent heavy wall steel tubing. The standard headers use 2 1/2" tube. The big tube headers use 2 3/4" tube. By using large diameter exterior tube this leaves a generous water jacket area that runs the entire length of the tube. This is essential for a long service life. Next the exterior tubes are mechanically etched prior to assembly. During assembly the complete header is TIG welded and a custom alloy welding rod is used in all critical areas. Finally a corrosion resistant silicone ceramic coating is applied to the interior of the header while the exterior receives a black power coat finish. Colors are optional. Headers come complete with aluminum water distribution tubes, gaskets, hose, clamps, bolts etc."
The salt water versions use a better grade of stainless on both the inside and outside tubes, 316L verses 304L on only the inside tubes of the freshwater versions, Smitty

I have had good luck with mine. 10 years in fresh water. They good power and last. Mine are the steel outers with ss inner pipes.