What is the equivalent RAL paint code for Munsell 3Y7.8/1.1?
I cannot give you an answer. First of all there are different types of RAL designations, some of which are not related to colorimetry. Some RAL designations are directly related to CIELAB coordinates. If you are looking for one of those designations, then you could convert from Munsell to CIELAB (GretagMacbeth provides software that does that) and then from CIELAB to RAL. Both these conversions are addressed in this FAQ.