I was just reading an article about how spart arrestor's on dirt bikes keep carbon particles from being expelled from the exhaust and igniting things.  Is this a concern on an off-road truck?  Or is the muffler so far from the engine that the hot carbon doesn't make it back that far?

I believe between the catalytic converter and the muffler just about everything that would catch on fire is stoped.  I could be way off though.

I think in any u.s. national forrest you are supposed to have an approved sparkarrestor like a supertrap,most of the time the rangers are to lazy to check or too busy, there is a couple of people in my heep club that run them and you can also dial in the amount of back pressure you want by removing or adding the plates to them, I run two of them on my buggy, not cheap but would cost more to put out a large forrest fire, you can also start a fire by running over a rock and breaking it in two  :-/

Turbochargers qualify as spark arresters,
and as a muffler too  

Wild

I assume that dirtbikes and other 2-strokes have spark arrestors because the pipe is hallow AFAIK... a muffler and cat should do fine.

you running a diesel now goodie ?  

with carbed rigs the exhaust runs soo much cooler than the f.i. rigs of present day, i'm sure it won't be long befor they change the rules for newer rigs, the forrest service rigs around here remove the cats because of the fire danger.

Diesel    No, not yet, but
I'm looking at the ways I
might get a Diesel in there

Wild

Yes, it's a concern. A straight thru muffler can attract unwanted attention.

To wheel in Michigan you must have at least one of the following:

- A reverse flow muffler (stock like)
- A catoletic converter
- Spark arester

Michigan sees any of these as a spark aresting device.

But we also have a noise level also 90dbl's I think.