Firewall markings help!!

[sameyrasmea72]

I am going to put the markings back on the firewall of my project truck, and I have gotten everything figured out except for a couple areas. This is for a 72 and it is the outside markings on the firewall and in the very center behind the engine(see pic)

It is the 4T markings that I am not sure about. I have seen some that read
2T and some dont have any thing there. And sometimes it is backwards and say T4 which is not really important, but I have seen it. I can find no Rime or rhythm to this. I have seen both both on swb, lwb, BB, SB, fleets, steps on so on. I thought if might be the paint scheme, but that is not the case either. Any ideas what this actually stand for????

The second area is the 3-digit # behind the engine. I don't think I have ever seen the same 3 #'s on any truck.

Thanks .......Jason