Sorry I completely missed this comment. I like the idea of the OEM oil to water cooler. Since Im not driving on the track or going anywhere too hot it should be good. Ill run a thermocouple on the sump and see what its doing.
What size plugs do I need for the old lines?
I'll upload some pics of what I did with the OEM cooler to the great oil cooler thread so they're in the right place to be easily googled.
As for a thermocouple, if you REALLY want to know what's going on, stick the thermocouple to the center bottom of the oil filter - that gives you oil temperature from the oil pump outlet. This matters because the oil doesn't actually circulate all that well in the pan unless you're cornering hard (even less well in a gated pan), and (because of the thermal viscosity effects) the hottest oil makes it back to the pump inlet quickest. Also, if you think about it empirically, you care about the oil about to enter the engine much more than the oil in the bottom of the pan that may or may not be going anywhere soon.
The NACA ducts, side scoops, and lid openings mean there's a pretty good amount of air moving over the oil pan at speed - it does passively cool some, which can be observed with a hot engine sitting still versus driving if you have a pan oil temp pickup.
That said, I'm using the bottom-of-the-pan pickup for the gauge thermistor. I know that this is slower to warm up than the supplied oil is, but there is an essential relation. I might well put a thermocouple on the oil filter just to see what the warm up time constant is between the two points.
I didn't use threaded plugs on the lines at all - I cut a couple of pieces of wine bottle cork to about the right shape and then zip tied them into the fittings, then zip tied the fittings up out of the way (one through the engine mount, one onto a water hose, IIRC. Yes, they'll probably drip a tiny bit briefly, but then so have some other things under there.