Looking at the photo of the T43 load, you can see two triangular or wedge shapes underneath the rising track. They appear to be steel, because they are relatively thin and appear to have welds on the bottom. If so, that means they are likely attached to a long steel tube (you can't weld steel to wood). At the end of the thing I'm calling a steel tube is a ramp-looking object. Notice that its width is about the same as the pair of steel triangular shapes.
OK. Please note that that steel tube is directly over the car side, for good reason, I think. And also note that it is NOT directly under the track. It is under the inside of the track and of the inner road wheels only. While this arrangement loads the car itself nicely, it doesn't look so swell for the tank suspension.
So I think someone thought it wise to put something under the outer road wheels, also. The COULD have used another piece of steel tubing. But it looks to me like they used wood. I can see what looks like knots in the wood. I can also see what look to me to be two or three holes in the wood, where I would have place bolts to retain the wood. It's possible they weren't used, however. I also see three cables or ropes or strings hanging from stake pockets.
Height of the load was about 14' - 10". PRR had boxcars with a max height of 15' 3 3", at the time. So vertical clearance doesn't look like a problem. Width of the M103 is 12' - 2". The max width of an F30 was 10' - 2". I am just not seeing the track overhanging the stake pocket by a foot, in the photo. I see the overhang as about 4", which would give a load width of 10' - 10", not 12' - 2". A puzzlement.