StiLL WILL: STi<1 summed it up well. GReddy block adapter part #12002801 is the one to get and was the only part we needed that was not included with the Defi gauges. BTW, that third large port is threaded for M12 sized sensor -- the other two ports are 1/8PT. The Defi oil pressure and temp gauges come with 1/8PT threaded sensors, harness connectors and long enough shielded cables (but you've got to be precise with your cable route) to reach from the oil filter location to inside the car using the grommet on the passenger side engine firewall. The way the Defi wiring/hookup from the sensors to the control unit works is very clean. I'm sure the other quality gauge manufacturers put together great packages as well.
Nick: Velcro strips/two sided tape is the recommended attachment method.