Not sure on the 7th gens, but I know on the 5th and 6th gens you remove the OEM oil sending unit located just above the oil filter. It is a one-wire sensor and is removed using a 15/16 socket.

I personally did this and I had a local fittings shop make me a 1.5' steel braided hose with male ends on it with the same size and thread pitch as the hole in the block that the OEM sending unit uses. I screwed my steel braided hose into the block, looped it and then put a 'T' fitting on the other end and ran that to the firewall. At the firewall I put the Autometer sending unit on one side of the 'T' fitting and then the OEM sending unit on the other. You might have to extend the wiring for the OEM sending unit, but I'm not sure - I did on mine and another I did.

Zip tie the whole thing (t-fitting, OEM sending unit, Autometer sending unit) to the brake lines on the firewall and wire up the Autometer gauge.

You should really do it this way or very similarly to it because the line that runs from the block to the T fitting will absorb the shock and bounce of the engine. If you were to put the T fitting right on the block, the weight of the sending units could cause the whole assembly to rip out with the movement of the engine and then you're in a world of hurt.

That should do it!
hih

:edit: be sure to Teflon tape everything!