If you get a mechanical gauge... get the copper or stainless lines...

Also it could be dependant on what gauge you're looking for. I have used both types is harsh environment and they've worked well.

 

Jason, the 2 1/16" gauges fit right in the vent holes. I'm using electrical gauges. I'll try to dig up some pics of the senders.....

 

howdy,
i use electric because the mechanical oil line fitting became loss once and my radio doesn't work rite anymore.

 

Here's the water temp sender.......

 

And the oil pressure senders...........

 

I usually use mechanicals, they seem to be a little more accurate . For the water , you can either tap the hole below the thermostat housing out to 1/4" or 3/8" pipe , then use the adapter included with the guage . I found a supplier for the 1/8'x28 to 1/8"x27 adapters to fit the oil senders in , works good . The stupid metric adapters are almost $4 each, but they do fit properly .
Sarge