The MGB parts book I have relates to the later 1976 rubber bumper cars and the part numbers for the valve guides are inlet 12H 222, exhaust 12B 1339 . The BMC 1.5 diesel parts book I have relates to the J2 van which was fitted with 1500cc and 1622cc petrol engines plus the 1.5 diesel . The exhaust valve guides on the petrol and diesel engines are all the same part number namely 11G 193, The inlet valve guides are different namely 11G 313 for the petrol engines and 11G 193 [ same as exhaust] for the diesel.
I also have a Brown Brothers Motor Factors catalogue from the early 60's and looking at the part numbers for the 1964 MGB exhaust valve guides and the 1963 J4 1.5 diesel engine exhaust valve guides and they are the same namely James part number G2616S .The actual valves have different part numbers .