The orifice hole diameter is the same (#24) on both the OEM 182a and b. It
is how the orifice attaches to the burner box that is different.One fridge
has a nut welded on the inside of the burner box and the other has a brass
nut that screws on, on the inside.Both attach the orifice to the burner
box, but in ways that make the orifices non interchangable.

I talked to a guy named Ed Lee senior. at Marshall gas controls.He said
these appliances will operate using a rather wide range of pressure. I
think it was about 9.5 - 11.5 inches of WC. A lot lower pressure than I
thought would work. Same preformance throught the entire range of
pressure. More is not better. This old Dometic may work better using a
slightly lower pressure.Who knows.