[piecesparts]

I may be missing something here. You told us that the truck was a 350, but never talked about the carb brand, the size of the carb, what jets are in the carb, or what the timing is set at, type of intake on the engine, or what temperature of T/stat that you use. There could be changes made here that could make it smell less like an old dump truck and more like a well tuned machine. What grade of gas do you use and what your spark plugs are set at. If you consider a multi-spark unit, like a MSD 6AL; you can get a more complete burn of your fuel since it keeps sparking through the fuel burn. What heat range are your spark plugs and are they burning at the right color? A good set of low resistance spark plug wires will help give you a better burn and a little more HP.

I personally would not put cats on the truck, I would consider a good set of mufflers---I use the Magnaflow stainless mufflers, since I used up several Flowmaster mufflers and had to replace them on a regular two year basis. This was on more than one truck, too--so it is not how the truck was used (daily driving and lots of highway use) Do you have a full exhaust or does it dump out under the truck? There is an advantage in the longer pipes, to get a good purge of your engine's cylinders and give the exhaust gases time to collapse and complete the burn of the fuel. Are you getting plenty of air through the carb to get the proper air/fuel mix for a right burn of the fuel. If your air cleaner is restrictive, then the fuel mix could be rich.

If you have a cam in the engine, then you may not be running in the right air flow area of the venturis. A cam can make you set the idle up to keep the engine running and cause the butterflies to sit in the transition area and not in the idle area, which would make your carb run rich.