John,
That plate bolts to the bottom of your stock intake. It has pipe fittings as seen in the picture. The plan is to circulate water through the plate, which will transfer heat to the intake. Most common takeoff point is the driver's side of the thermostat housing that feeds the upper radiator hose. GMC's and 261s use a housing that is already drilled and tapped - or you can (Carefully) drill & tap your old one. Put a pipe fitting in there and run heater hose to fitting #1 on the new plate. Cut your heater return hose and put a "tee" fitting in it, then connect that "tee" to fitting #2 on the plate.
Your temp gauge sending unit threads into a hole in the top of the cylinder head. No need to change anything there.
You can also do this with copper tubing which actually makes a pretty clean installation. I saw a 235 done this way at the Bowling Greeen show today. The tubing was bent just right, run behind the headers and looks a lot cleaner than a bunch of black heater hose hanging off the side of the motor.
Hope this helps - maybe somebody out there can post a picture of how they did it.
