Hi Paul,
Temp sensor locations are easy on the LS motor.
The factory coolant temp sensor is in the front of the passengers side head just next to the exhaust flange. If you check the back of the drivers side cylinder head there is a corresponding hole with bung threaded into it. This has a 12mm thread and you can make an adapter to take it down to 1/8 NPT or BSP depending on the sender you are using.
I'm using mechanical gauges and the temp senders have a capilary tube with a bulb on the end. This required a bit of messing round to get them into the LS motor but it's do-able. Here's the back of the drivers cylinder head where I've drilled out that 12mm hole and re tapped it larger to take a larger adapter I made. A M12 to 1/8" NPT wouldn't just screw straight in without the extra work. You get the idea. I made one for Phil Neall some time back.
Oil pressure is easy too. There is a crossover above the
oil filter where
oil is ducted out of the sump and back in again. I reckon it is an adaptor for an oil cooler. It already has a boss cast into it that can be drilled and tapped to 1/8" NPT. I used mine with an AN#3 adapter so I could run a braided line back to the mechanical gauge. An electric sender could be threaded in just as easily.
Oil temp is easy depending on which motor you have. If you have a US crate motor it is likely the sump is already drilled and tapped for an oil heater. In extreme cold temps there is an option to plug your car into an electrical outlet and keep the oil in the sump warm overninght in freezing temps. I just unscrewed this heater and made an adapter to take my mechanical oil temp sender.
If it's an Aussie motor it may still have the boss in the casting. Otherwise the sump is plenty thick enough to drill and tap a hole directly into it. I would take the sump off to do it but even that is an easy job due to the reusable O-ring gaskets.
Hope this helps.
Cheers