Phranq, in your fuse box you should have 3(or more) different fuses. One for the fuel pump and two for the fuel injector assembly. Injector fuses will be labelled INJ A, B, etc.
What I did for my Sierra was I bought fuse taps which go in the place of the fuse to make it remote. You still use the original fuse it just gives you a clean place to splice in a wire without permanently modifying your wiring. I spliced a wire into the tap and ran the splice to a switch in the cabin for each fuse(3 total for my 4.3L). If you just want to shut them all off then only wire in a switch, if you want to be able to hybrid, also add a Pulse Width Modulator on the Fuel Pump fuse.
Here is an eBay link to the fuse taps I used. They are not the Add A Circuit taps. Splice on one of the wires a connection to a switch.
Repair Car Fuse Holder Connector - Mini ATM, 32V 20 Amp, 16 Gauge Red Wire Cable 711181802160 | eBay
If your engine has the Spider type injectors it’s not advised to do this, they depend on consistent fuel pressure so it’s either On or Off, you can damage them with too low a pressure. The number 1 cause of those spider injectors dying is from people not replacing their fuel pump and filters and it affects pressure.
I’ll edit this post with some photos of my wiring setup, I don’t have a diagram I’m just not that kind of guy.
For plumbing, I bought a silicone sleeve from an auto parts store that matches the throttle body diameter. My air cleaner didn’t have any natural tapping points to attach a woodgas line so I decided to build a whole new one and keep the original one unaltered.
I am still building the air cleaner for my Sierra but because my throttle body is about 3" OD I’m using 3" PVC pipe to keep air flow correct when on gasoline. 3"PVC is 3.5" OD so I used a 3-3.5 silicone adapter. Don’t use silicone elbows they collapse under vacuum, use PVC elbows. I am not going to glue my PVC but just use a single wrap of aluminum duct tape, so I can take it apart for cleaning.
I’m a little lucky with my actual air filter box because the MAF sensor is located on that box. You want your woodgas to come in after the MAF sensor to keep it from getting dirty. I am using a 3x2x3 PVC Tee and my woodgas is coming in from the 2" line.
Somewhere between the MAF and the Tee add a butterfly to choke down your air. You can also put in a valve to completely shut off the woodgas plumbing but I haven’t found it necessary, your mileage may vary.
If your truck has a pan type air cleaner, or any of those sound dampener tumor looking things in the house you could use those to bring in the woodgas if it has a neck that is close to a PVC pipe size.
Most V8 guys have found two woodgas lines coming in helps out a lot, plan to include two lines.
If you want anything more specific you can PM me I’ll be glad to help you out no charge. Pictures of your engine bay would really help me strategize.