For oil pressure, you can either put the GReddy sending unit where your stock one is and run w/o the stock idiot light, or you can tee off the stock sending unit location for both. The bes way is to run a line to a tee mounted on the firewall to isolate it from engine vibration:



Although some tee right off the block:



Teeing right off the block hangs a lot of weight off the back of the block on a pretty small fitting, and with enough vibration, it could snap right off, which you probably wouldn't want.

For water temp, people often install the sensor in the coolant bleed port(if you have a B series). My D16Y8 doesn't have a bleed port, so I elected to use GReddy's 34mm water temp sensor adapter, which splices into your upper radiator hose. I had to switch to larger B series hoses to fit my PWR radiator, so the 34mm adapter fit perfectly. It was too large for my stock hoses.