I want to install an adaptor on the upper radiator hose that goes to the thermostat

http://cgi.ebay.com/38mm-Water-temp...arts_Vehicles_CarParts_SM&hash=item335ac41878

would this fit?
I don't know which size I need (34-38mm?)
my car is a '96 75MPI
thanks

why you need that?

It wont give you a true engine temperature because its after the thermostat. But for a 2nd gauge it could be amusing.

To answer the question the hose internal is about 6mm less than the external so measure and do the sums.