MainJet,
I dug around and came up with this old post. (thanks Coilover).
"The long capillary tube temp guages are a little pricey but you can grind a flat spot on the left rear water runner on your intake, drill, tap, and screw in a temp bulb fitting. You can see a picture of this at
http://www.msnusers.com/Evanscars Click on "pictures" and then go to page 2 and it is picture S10-054."
The link doesn't appear to work anymore. This trick was done on a 350 Chevy engine.
Stuart