We use a mechanical oil pressure gauge and an electric water temp gauge. At one time I used a mechanical temp gauge but the capillary tube is difficult to run and easy to damage. I use autometer gauges the mechanical oil pressure gauge which is liquid filled to help resist the vibrations which may not be necessary they (autometer) also have a trick low temperature electric gauge the I really like because it helps keep the launch temp accurate.
A note of caution about using electric temp or oil gauges they must have a good ground to be accurate and the motor plate,especially if it's anodized makes for a poor ground connection to the chassis. I run a seperate ground wire for my temp gauge and the transbrake solenoid I also ground the battery to the starter. My Dyno guy has seen on incidence of picking up power by running a ground wire from cylinder head to cylinder head and back to the battery,I have not tried this myself but it makes sense that the ignition needs a good ground path too. You also need to make sure that the sending unit is not at the high point in the cooling system or you may have to run the water pump to get an accurate reading and you don't want the sending unit in an air pocket.
If you use a mechanical oil pressure gauge I would use a #4 AN Braided line as it will not dampen the response of the gauge don"t use copper, aluminum or steel may be ok but the #4 AN (Earls/braid covered rubber)is easy to route and has been reliable.
I also run a large 30# Idiot light (Longacher or Speedway motors) I also have an Idiot light for the trans brake that lets me know it's energized and I have a shift light that continues remind me that I have overreved the motor on the burnout
As far as wiring goes make sure that everything can be shutoff by
one switch [/U]and that it has a sufficent aperage rating to handle the load.
I have seen a couple of cars equiped with a cable to turn off or on the main power switch with a lever in the cockpit which I think is a good idea especially when I'm strapped in ready to go and I forgot to turn the damn switch back on
I don't run the starter current thought the main power switch it will eventually fail and if you using an electric fuel pump put a safety pressure switch in it circuit.
Well that probably a lot more info than you wanted anyway
but if you have any questions let me know.