Many are in the filter head.

Sorry I should have been more specific. Im running 1996. 454 Merc's. Are you T'd into one of the rubber hoses or did you find a plug there to remove? Thanks for the insight!

Haven't done it yet, but while I'm changing out everything, and looking at tapping a 1/8 NPT on the opposite side of where the line comes into the filter housing and before the cooler

Im running Mercury, nice thing is, you dont need to figure out where or how to mount them

Mine are at the filter head, measured after cooler, I am putting them in my pans also and going to have a switch to monitor both places..

I put these on last year and they worked great.
http://www.improvedracing.com/oil-th...85f-p-212.html

Something to consider is if they offer optional temperature replacement thermostats

The mercury racing I have only offer the 210 deg stat, it's sourced from a 90s M series BMW. The road racing crown has machined a solid billet replacement that keeps it open at all times, which does us no good.

For what its worth I have been running the Perma-Cool oil thermostats with 3 1/2" x 24" oil coolers for 8+ years now. They have worked great and solved my oil condensation issues. I know they don't look very fancy but the thing I liked about them is that they use a standard car radiator thermostat "pellet" , so you can pick the temp you want them to open at anywhere from 140deg - 220+deg. Just buy the desired temp radiator thermostat and cut the pellet out of it, remove the snap ring on the perma cools and swap it out. Takes 5min... There are 2 in the swap shop right now (not mine) if you want to see want I am talking about. Also the ones that Full Force originally posted look like billet body versions of the same thing (they definitely plumb the same) so maybe you can do the same pellet swap with those. Anyway just trying to help, I know I don't post on here very much...

Oh and I settled on 195 deg pellet, my oil temps warm up fast and then stay between 200-215 no matter how hard I run it or what the water temp is like. my sensor is at the input to the oil filter head (before the thermostat or oil cooler ).

Thats funny you mention that. I have a mercury oil thermostat element on my desk. Was looking at it, and it looks like a regular wax type element. Id like to see if it will match up to a typical auto stat element