Does anyone know what the physical difference between the M-54 and the M-813 trucks. I want to use the hood and front end for the M-813 from Real Model to put on the AFV M-54 that is coming out. Or should I wait if there is a chance that AFV club might make a M-813?

There are a lot of small differences, but the primary outwardly visible difference is the air cleaner (left vs right) and the length of the hood and grill, which is longer and larger for the 809 series vs the M54. This was primarily due to the larger engine size. It might take a lot of work to make those changes.
VR, Russ

Russ has pretty much covered it. The M813 is 6" longer due to the longer hood/engine area. The wheel base (179") is the same on both.

Here are drawings to compare them.

M813


M54

Gino's drawings point out the differences. But It also depends on what truck you are trying to make in the series-- the expandos were longer, and some 809 series trucks came with the larger single rear wheels vs duals. A straight cargo truck would probably match up pretty well, and the length might not be too noticeable, but other trucks might require quite a bit of work.
VR, Russ

He is talking about a standard M813 cargo truck and a standard M54 cargo truck, so apples to apples. Different models of each series would have different dimensions, but they should be pretty much the same differences, if that makes sense.

We will have to wait an see how the AFV Club M54 is broken down when it comes out, but my guess is that it will be like their M35 and have front frame extensions for the winch. By using these front frame extensions (cut down to 6", or about 5mm in 1/35) and not installing the winch, you would have the right frame length for an M813 since all the added length (6") was in front of the front fenders (see drawings above).

M54


M809



M923

Take note the M800 series had two different grill styles: the early one made up of welded slats, and the late one, tube+mesh style.

Early:




Late: