I've put mine in a couple of places.
1 - If you still have the bypass hose on then I drill and tap a hole right beside the thermostat housing so the sensor pokes in from the side of the head.
2 - If you have eliminated the bypass hose then you can buy a big bronze plug to plug the hole in the head and drill and tap it to accept the sensor.
3 - You can buy one of those inline things from SLP and put it in a hose.
sled_guy