I respectfully disagree. Having two throttles won’t really make anything harder, you’ll simply have to pick one or the other - not both at once. Then it’s no different than driving with a single throttle.
If you needed to use both throttles, and the clutch (or brake) all at once, there are other options such as hand throttles or Max’s linkage (below). Or simply mount them close together and hit them with the same foot.
I’ve driven plenty with dual throttles and seldom used both at the same time unless I was cruising and needed extra passing power… at that point you’re not braking or clutching, both feet are free.
Yes, I do like Max’s linkage solution and plan to try it out someday. Here’s a video, showing the principles:
The advantage of two throttles is that it gives you the smoothest way I know to run hybrid. It even beats fuel injection in this regard. It puts the operator in full physical control of the exact ratio of gasoline to woodgas, no computers or fuel pump voltages to fiddle with.
For a full size truck like you’re planning to build, running hybrid will be a consideration - you won’t be able to run 100% woodgas all the time, not at high speeds.
You can’t really blend in gasoline when you go through the top of a carburetor, as the float bowl needs to be drained out before the woodgas will run. This means for carbureted hybrid running, your only real option is to add the woodgas under the carb.