Valvoline Semi synthetic 10 w / 40 Engine Oil

Hi all. Im trying to source valvoline semi synthetic engine oil for my 1990 non turb mitsu manual GTO as recommended by Joe. My local suppliers ended up with a 5 l bottle that said synthetic on it and says he cant get the semi synthetic marked bottle and they both have the same ACEA A3 /B4 code on the front of the bottle. Been trying on line but struggling to source and check which is the correct one. Can any one help with correct code and to suggest reputable reliable supplier. Many thanks