[Jim Vander Wal]

Can you pull the original and take it to NAPA. I believe that it is metric and they'll have a good collection of plugs.

Just measured the plug the original radiator from SPO 1855, a 2004 car. This is the same plug as is in SPO 2584 (2007). It is 10 - 1.5 and about 20mm long. You can find that at a hardware store except that the plug has a sealing surface and a copper washer. A 3/8" copper washer (NAPA) would work and a standard bolt may as well.

Otherwise search for Superformance and get the main office. Ask for parts, don't immediately remember the man's name but he was helpful and called me back after one request for assistance.

Jim
1855 & 2584