Yes, that will work fine.....but i think it would be far more important to
know what the oil temp is coming from the engine and not the cooler.

My thought was that, if the oil coming off the cooler is very hot, then it
is time to shut down and cool down.  If the oil coming off the cooler is
reasonably cool then if should be safe to continue on.  I am also
contemplating installing a 6-inch fan on the oil cooler. Just a note.  We
are going to be pulling a trailer (size unknown yet but around 30 feet.) I
am also planning on getting a transmission cooler with a fan.

IMHO it belongs on the input side of the cooler not the output. You
are interested in how cool the oil is in the pan. However, as long as
you know what to expect for readings either works. I just use the
input side...

Dat said, there are some manifolds that are designed to work for these
installations. A standard T fitting might bolt together, but you are
either not going to have good flow over teh sensor (because it is too
high in the T, or the sensor may partially obstruct the flow. The few
tiems I tried T setups, I didn't like the results--they were not
accurate.

Again, IMHO (and perhaps not so humble, either) I prefer a direct to
oil in the pan. I've gotten the most accurate readings with that
configuration. I mount in a protected location, often the rear of the
pan is good, depends on installation. Some smart gauge maker should
make one that fits on the end of the dipstick... <g>

   Yes, that will work, as long as the T is not too
deep.  If it's a long reach from the tip of the probe
to the oil flow, the oil will pocket there and cause a
(slightly) inaccurate reading.  OTOH, if the probe tip
extends directly into the oil flow, it will probably
obstruct the flow enough to be a problem.
    Like you, I prefer to measure the oil temp as it's
being fed to the bearings.  That's the most critical
reason for checking the temp.  If it's too hot in
there, it won't work well and you'll score the
bearings.  Checking the pan temp is OK too, as long as
you realize that the oil will pick up heat as it flows
down from the heads and drains in to the pan.  So your
tolerance for heat in the pan is a little higher than
heat to the bearings.   The temp as it heads in to the
cooler will be almost the same as the temp in the pan.
 It will pick up a little heat through the pump, but
not much.
    I don't think it really matters where the probe
is, as long as you are aware of how to read and
interpret the results.

Thanks for all your help