Mount them where you see fit. Search for Mike "SuperSubs" build thread, he made a bad-ass center console to mount 3 gauges.
As for wiring, again Search "Google" for the wiring diagrams for your gauges. There are generally two ways to wire a "standard" pressure/temp gauge. That's a SINGLE WIRE install, and a DUAL WIRE install. Single usually involves grounding out (to a GOOD engine ground) the PROPER wire and then running a single wire to the gauge (which sends the signal) and also tapping a GROUND near where the gauge is installed. This halves the amount of wires you have to running through your engine bay/firewall. However you need to make sure you have good grounds in order to achieve reliable results.
For best peace of mind, just go the DUAL WIRE/2 WIRE install method. (where you run two wires from the sender/probe all the way to the gauge).
I suggest several things. For wire, a FINE BRAID/TWIST wire is better than a coarse/thick wire because of the work-hardening that makes the wires want to crack and become brittle from vibration is much less with fine/thin wire. Secondly, I might suggest doing what I did when I had electric gauges, I bought some hose (vacuum), I think in 1/4" or 3/8" diameter, sliced it ALL the way down the side so I had a C shape, and sleeved it OVER the probe/sender wire. This gives you a really good heat/abrasion shield. This is cheap, there are actual sleeves that you can buy from Summit/Jegs, maybe NAPA that are designed to go over wires/tubing/hoses that reject heat/abrasion and are made from FiberGlass/Kevlar etc.
As for where to come through the firewall... well, wherever you see fit. You could try coming in where the engine wiring harness comes through the firewall. Or you could be
SUPER SUPER SUPER SUPER careful and drill throught he firewall in a discreet location and
MAKE SURE TO USE A GROMMET, and use Toyota "Form-In-Place-Gasket" Sealer to seal the grommet in place as well as seal the hole closed again.
It's all up to you. There's also a Lotek 2 pod A-Pillar gauge available for cheap as well.
http://www.gaugepods.com/toyota.html