I did a deeper dive on this and put a sweet little chart together. Following is info from the service manual.
What I've found so far is that the bolt head markings on Mitsubishi Bolts don't correspond to anything in the real world. JIS bolts seems to follow metric bolt hardness but I question that a little bc when does that ever happen?
The max torque spec between Mitsubishi 4 and Metric 4.8, Mitsubishi 7 and Metric 8.8 are almost identical. These are in NM and for dry bolts.
Also, know that the thread pitch between what is specified by Mitsubishi and the other bolt chart don't match 100% but they are close. It is really challenging to find identical bolt spec listed listed.
The reason I dove into this was bc I am constantly replacing bolts on the van. I typically purchase metric 8.8 bolts but wasn't quite sure if that was the right thing to do. I am in the middle of the 2" body lift from Dreamworks and the washers are all made of bubble gum which had me questioning the rest of their bolt choices. I couldn't get a proper torque spec on anything due to bubble gum washers squishing and ripping out during tightening to factory spec. It had me concerned hence this deep dive.
Moral of this story, there is a bolt spec, follow it, don't buy bubble gum hardware or your body and chassis might separate while driving down the road which, while exciting is not not going to be welcome.