The good part about pedestal mounts is they articulate freely and allow you to position the radio stack to suit your needs. What I don't like is the way they wobble around, especially with 3 radios. I have a 4WD truck and use it as such. What bugs me the most when I'm flying down a class 3 byway is to have the radios swaying and banging around.
If you have 3 radios, you'll have to co-join all together regardless of what it all mounts to. Do this. Decide how you want the radios stacked. Cut 2 pieces of heavy (18ga) sheetmetal. Drill holes for the mounting screws of the radios in the sheetmetal. If the radios are different widths, use nylon spacers and find longer screws to fit the short radio. What you should come out with is a nice tight radio stack held together with the sheetmetal straps on the sides.
You can now position the stack in the truck and see how it fits. If you want to use a pedestal, use the mounting bracket of the bottom radio under that radio (with the sheetmetal still under or over the mounting bracket) and bolt the mounting bracket to the pedestal. Or you may want to forgo the pedestal and bend up your own custom mount to fit the truck. It's kinda up to you on how sturdy it is and how nice you want to make it look.