Sound reduction panel

I am pouring over ideas on how to make my TNT quieter inside my box truck. I have the plans in-place to reduce the blower noise, but I still contend that it is that motor that will need some attention if I am to have success. Outside of a good working muffler, there doesn't seem much potential beyond that.

Space isn't a big problem for this project being in the 8 foot tall box, so I had been thinking about converting a motorcycle muffler to the motor or even an automotive muffler. Of course, then you will just hear the motor rattling away as they don't have thick blocks to begin with.

So, I am contemplating a sound panel design that would consist of a louvered panel attached on hinges like a swing out panel door. I would line this door panel with sound absorption material up to the height of the machine. It would reduce the surface area which should reduce the noise, but I am not sure how much it would affect the cooling. I don't know how much air flow this motor really needs to survive.

It would be a panel that was about 4x4, so the louvered section would still provide some air, plus the heat could rise another 4 feet above the machine and there is far more space around the machine than their would be in a van, so maybe it would work. I think having the roll-up box doors front and back is a huge benefit here and far superior to the air flow found in a van.

Simply open it up for access to controls and then close it up when operating. My hoses are running to a live reel in the compartment next to it, so I don't need any access holes.

I guess this is similar to a diesel generator with access panels....same concept that seems to work for them.

Good idea or bad idea? What concerns should I be taking into account?

The motor needs all the air it can get period.
But you could have a duct going to the front of the engine pulling fresh air from outside. Then you have to get the hot air out of the van. As for the muffler idea what about running the exhaust through the floor and then into a muffler/silencer or maybe even into the vans muffler I'm sure it has a large muffler then a long tail pipe that should help a lot.