Okay, let's talk about options for flight instruments a bit. You can go with the instruments rendered on your display. You can use an assortment of simulated instruments. You might even plan to use a few real instruments. Let's take a poke or two at each approach
Hang with what ya got
Simply sticking with the instruments drawn on your display has a lot going for it. For one thing, you've already got it, already paid for it; a HUGE advantage. It's also already tied into the simulator software, i.e., no interfacing heartburn. If you don't quite like the panel layout, you can change it. (Well, you can with some of the sims like MSFS, X-Plane and Fly!) On the other hand, it lacks the feel of the real thing. You KNOW you're looking at a computer display and not an instrument panel.
Rats!! Another hurdle on that sprint to suspending disbelief.
One relatively easy improvement is to place the monitor behind a cutout in an instrument panel mockup. This can work particularly well if you're building a glass cockpit. Still, there can be a lot of panel space to fill up, so you might expect to use several monitors. If you take this approach you might take a close look at the 15" LCD monitors coming available. Prices have dropped. Some models have a removable stand, and because they weigh considerably less than their CRT cousins, demands on the design of a replica instrument panel are eased.
If you're not satisfied with what you've got, you might consider commercially available simulated instruments.