I recently bought the thermo and bracket from Peek Performance here in DC.
The spring is not a tough item to come by as you can get a throttle return
spring to do the job. Make sure it will return the fins to open if the 
thermo fails. Junk yards are a gold mine for this stuff also.

                                              Steve
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\  Steve Walker                                     '64' Micro "Amelia" /
/   E-Mail: Walker4@ccfsun.nrl.navy.mil                 Rags rule!!!    \
\    Voice: (202) 767-6978                                              /
/      Fax: (202) 404-6168                                              \
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