Ya, I would keep the box for traction weight. You do want to be light but not too light. I ran about 3 years ago at a local fair. I ran stock class with my '82 Jimmy. I left just about everythign in it that I normally run except for a big cooler. At the time I had a tired 305... I ended up it the top 2 and got beat out by a SWB Chevy, but I gave him a good run. What you need is good reaction times and traction. I got good traction because the 305 couldn't really break the tires loose but yet it got the Jimmy movin. I also still had on my top and rear tire carrier with spare.
If you have a good runnin engine that can launch hard you may benefit by adding some weight! Adding ewieght you can add traction. The rest of the guys will go for all lighteweight but then you sacrifice traction and if you are spinning the tires you're not grabbing and going.
See if you can get a look at the track a few days before the event.. I forgot to ask about what the track type was like..... But I just re-looked at the title and you said mud drags. So you may want to think a little different than what I said above. THat worked great that night on a dirt track that was hard with just a little loose stuff on top. That same night in the bogs, I think I got 5th... I didn't have the HP to get me through the mud fast enough. And in the mud I would try and go as light as you can but not too light. Keep the bed. Try and find a area where you can practice your launches and maybe play with different weight set-ups.
Just my .02cents. Good Luck! /forums/images/graemlins/thumb.gif