I have searched for that, but it does not work. All the documents just mentioned We do have some J2M which are equipped type2/5 30mm cannon, but no details.
I believe it can choose to replace just 2 or 4*20mm cannon, as the title photo shows that J2M can still have 2* type 992 cannons, and according to the"Japanese Air Weapons And Tactics, 1947 (U.S. Strategic Bombing Survey) : Military Analysis Division : Free Download, Borrow, and Streaming ...
I found a very special version of J2M, which has 30mm guns, and it looks like type 5, but I can only find some pictures. I'm also searching for general stuff, tech, usage manual, and Blueprints. especially regarding its weapons.