Full instrumentation is mounted in an aluminum dash board which looks nice and won't rust and doesn't need painting. An automotive ignition switch was installed to hook directly to the engine electric starting circuit.
I used aluminum check plate for the bottom floor pan. This material is very rigid, light weight, and has the benefit of never rusting nor does it need painting. The check plate is fastened with stainless steel 1/4 inch bolts through the bottom frame rails at about a 12 inch spacing. When mounting to the frame rails, clamp the cut check plate to the underside frame rails and hold it tightly in place with a bunch of "C" clamps. Now drill through both the frame rail and aluminum plate with your drill so that all the holes will line up perfectly. The raised pattern of the check plate creates a natural small space between the check plate and the frame rail bottom so water can still drain out if it collects in the frame cavity.
If you are wondering how you cut thick aluminum like this, well that's very easy. Aluminum is a non-ferrous metal so you can use a conventional carbide tooth blade in a circular saw (skill saw). A 40 or more tooth carbide blade cuts through the aluminum check plate like butter! Using two "C" clamps, clamp down a thin wooden cutting guide to slide your circular saw base against to get a nice straight cut. Remember this stuff is not cheap so you don't want to make any "free hand" cutting mistakes! I find that the circular saw cutting method makes a much superior cutting job than an angle grinder which is hard to keep running straight and also burns up blades very quickly. Believe it or not, there are hardly any ill effects to the carbide circular saw blade and it can be used for many more cuts of this type. Now most importantly; NEVER, UNDER ANY CIRCUMSTANCES, EVER CUT ALUMINUM WITH A CIRCULAR SAW WITHOUT WEARING TIGHT FITTING SAFETY GOGGLES OR BETTER YET, A FULL FACE SAFETY SHIELD AND GLOVES. Cutting shavings could fly around and hit you.