'64 Nailhead valve cover plug

For you guys who have detailed the engines in your 1st generation Rivieras which have the rubber plug in the front of the driver's side valve cover, where did you find a repo plug for that? Cars Inc. has a couple listed but they say they're for '64 - '67. The last year for the nailhead was '66. Is the part that Cars is showing for the 300 - 340 engine? I don't want to destroy what I have to measure the hole so I can't go by their dimensions. Any help will be appreciated.

Here's a link to CARS part. http://www.oldbuickparts.com/catalog/1963-up-riviera-group-oiling-rocker-cover-plug-1964-67-buick-p-664.html

Ed

Ed,

That is the correct plug. The application is greater than yours.